Updated 11:19 p.m. - With the general election matchup against President Obama beginning to take shape, Mitt Romney swept a trio of Republican primaries in Wisconsin, Maryland and Washington, D.C. on Tuesday.

Romney strengthened his grip on the GOP nomination by virtue of winning the three states, the most competitive of which was in Wisconsin, a state seen as necessary for Rick Santorum, the chief conservative rival to Romney, to retaining viable hopes of winning the nomination.

M. Spencer Green / AP

Republican presidential candidate Mitt Romney declares victory April 3 in the Wisconsin presidential primary.

But Santorum vowed to press forward with his campaign, characterizing the primary as only having reached "halftime," while Romney kept his focus squarely on Obama in his victory party remarks Tuesday night.

Watch Santorum's speech on msnbc.com

"The president has pledged to 'transform America,' and he has spent the last four years laying the foundation for a new government-centered society," Romney said in Wisconsin. "I will spend the next four years rebuilding the foundation of our Opportunity Society, led by free people and free enterprises."

The former Massachusetts governor had looked to move closer to putting the drawn-out Republican primary behind him, and beginning a new chapter – the general election campaign versus Obama.

Watch Romney's speech on msnbc.com

Nonetheless, Romney had battled fiercely in Wisconsin against Santorum, who needed a win there to sustain his campaign heading into the next group of contests on April 24, which includes his native Pennsylvania.

Romney's victories came at a point when the Republican Party has shown signs of rallying behind Romney, and a general election that has shown increasing signs of shifting into gear.

Related: Romney cruises to big win in Maryland

That sentiment was reflected in Romney's celebratory remarks, where he made no mention at all of his Republican rivals, and rolled out a new refrain decrying "Barack Obama's government-centered society."

That came after an especially political speech this afternoon by the president, which featured pointed criticism of both Romney and the House Republican budget in anticipation of the general election.

"One of my potential opponents, Governor Romney, has said that he hoped a similar version of this plan from last year would be introduced as a bill on day one of his presidency," he said of the GOP budget blueprint recently approved by the House. "He said that he’s 'very supportive' of this new budget, and he even called it 'marvelous' -- which is a word you don’t often hear when it comes to describing a budget."

Related: Romney wins Wisconsin, moves one step closer to nomination

"It’s a word you don’t often hear generally," Obama added, to laughter, in a thinly-veiled swipe at Romney's personality.

Obama's campaign has also ramped up its attacks against Romney, portraying him as an ally of oil companies in a new television ad airing in key swing states.

Wisconsin Rep. Paul Ryan, the House Budget Committee chairman who emerged as one of Romney's most effective surrogate for Romney in the past few days, and a favorite among conservatives to round out Romney's ticket, fired back at Obama at Romney's victory event.

"We found out today that he's going to divide us in order to distract us," he said.

But there's still the unresolved matter of concluding the Republican primary. Both Santorum and Gingrich have defiantly vowed to continue forward with their campaigns, though their strategies of winning the nomination hinge on wresting the GOP nod away from Romney at the August convention. Both candidates have events on their schedules in the next few days, and Texas Rep. Ron Paul added new events on Tuesday in Texas and California.

Santorum emerged at his election night event to declare the GOP primary at its halfway point.

"This is why we came back to southwestern Pennsylvania: to kick off the second half," he said in a speech leveling sharp criticism of Romney. "Ladies and gentlemen, Pennsylvania and half the other people in this country have yet to be heard."

A total of 92 delegates are at stake in Tuesday's three contests, with 1,144 needed to secure the Republican nomination. Romney entered Tuesday having accrued 490 total delegates through March 24, and his margin over other candidates will grow as a result of tonight's wins.

But more powerful than the widening delegate margin has been the growing cavalry of Republican figures who had previously remained neutral in the primary -- among them, former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio and Wisconsin Rep. Paul Ryan, among others -- have gotten off the fence and endorse Romney in hopes of hastening the end of the primary campaign.

That group could swell in the three-week period before primary voting resumes in five Northeast and Mid-Atlantic states -- contests where Romney is favored, aside for a more competitive showdown versus Santorum in Pennsylvania.

APPLETON, WI -- With less than 36 hours remaining until Wisconsin voters may well hand to Mitt Romney another primary victory, Rick Santorum told reporters that a contested convention in Tampa would be "fascinating" and "energizing" for the Republican Party.

"I think it would be a fascinating display of open democracy and I think it would be an energizing thing for our party to have a candidate emerge who isn’t the blessed candidate of the republican establishment," he told reporters during a stop at a cheese shop and factory.

"I think that’s a good thing, it’s a good narrative for us," he said of a prolonged primary contest and floor fight.  "It makes this election a short election. The shorter this election in the fall, the better off we are, not the worse."

Santorum, who trails in public polls in the Badger State, faces increasing calls to exit the race and allow Romney, who's working to cement his status as the party's presumptive nominee, to focus on the general election.

But the former Pennsylvania senator, who spends much of his stump speech arguing against that premise, has vowed to keep the heat on his rival.

"Cutting this short and getting the wrong candidate is worse than making this a fight for the heart and soul of America and the heart and soul of the Republican Party," he told voters last night in Green Bay."

In Appleton, Santorum offered a lengthy explanation of his view of a contested convention, saying that the ultimate nominee would be determined by unbound delegates rather than by "power brokers" like in past cycles.

"That’s just not how the Republican nomination works anymore," he said of traditional "brokered conventions" of old.

Santorum also hopes that a strong showing in his home state of Pennsylvania in three weeks will re-inject an air of legitimacy to a campaign that most political observers now see as a sideshow.

"We're going to win there," he said of Pennsylvania. "The maps look a lot better for us in May."

But of Wisconsin, he only promised "a good vote ... a loud, confident vote from conservatives."

Down in the polls to Mitt Romney, Rick Santorum is up with tough new TV ad in Wisconsin, which shows President Obama's face morphing into Romney's.

The script:

“I’m Rick Santorum and I approve this message.

Female narrator: "What if I told you this man’s big government mandated healthcare included $50 abortions and killed thousands of jobs?

Would you ever vote for him? What if I told you he supported radical environmental job killing cap and trade and the Wall Street bailouts?

And what if I told you he dramatically raised taxes and stuck taxpayers with a $1 billion shortfall? 

One more thing: What if I told you the man I’m talking about isn’t him?

[picture morphs from Obama to Romney]

It’s him.

*** UPDATE *** The Romney campaign issues this response: “Rick Santorum is attacking pollsters, attacking reporters and attacking Mitt Romney. It is sad to see him completely lose his bearings and revert to patently false claims. Senator Santorum is at a point of desperation that he will say or do anything. It is pretty clear that he is lashing out at everyone around him in order to prop up his sinking campaign.”

With more endorsements by prominent Republicans and a new poll showing him leading next week’s Wisconsin primary, Mitt Romney is on the cusp of becoming the party’s presumptive nominee.

Yet it’s taken Romney far longer to win the nomination than most observers expected, especially against under-funded and under-organized competitiors.

Why?

Republicans and analysts point to several culprits: the proportional delegate system, Romney’s gaffes, his flip-flops, his message, even his Mormon faith.

But he's also been plagued this primary season by a Republican Party still in the midst of an identity crisis, which has made things rocky for the former governor (and former moderate) from Massachusetts.

First Thoughts: Romney to wrap it up?

A wave of conservative enthusiasm -- with the new “Tea Party” movement as its leading edge -- propelled Republicans to record victories in the 2010 midterm elections, which delivered them control of the House and gains in the Senate.

The new freshman class, though, demanded more purity from their leaders. The very enthusiasm that helped Republicans win back part of Congress hampered their ability to govern; House Speaker John Boehner encountered great difficulties in convincing the newly elected ideologues to join in legislative compromises.

These fratricidal squabbles continued into the presidential campaign, where conservatives have resisted, at virtually every turn until now, the opportunity to get onboard with the establishment-favored candidate who’s regarded as most electable: Romney. 

“There's clearly a bit of a crisis,” said former Delaware Rep. Mike Castle, a moderate Republican who was considered a shoo-in to win his state’s Senate seat in 2010 before losing a primary to the Tea Party-backed Christine O’Donnell.

“The division and savagely attacking of other Republicans when they don't vote the right way I think is very counterproductive,” added Castle, who is supporting Romney (ironically, along with O’Donnell). “I don't think that has appealed to some Republicans, and I'm sure it doesn't appeal to independents and Democrats.”

Other reasons why Romney has been unable to gel conservatives behind his candidacy are probably more technical. Republicans cite his campaign's shoddy work in courting conservatives, the new primary rules that prolong the nominating process, and the candidate's gaffes at key points in the campaign. Romney also struggled to shake his image as a “flip-flopper” at points in the campaign, an image underscored by a senior aide’s recent comment likening the candidate’s pivot to the general election to an Etch A Sketch.

But while Romney is hardly a perfect candidate for today’s Republican Party, such a mythical creature might not exist anywhere on the planet. In some important respects, Romney's troubles stem from a party that is re-fighting its internal struggles from 2010.

“I think it's directly attributable to the spirit of 2010,” said Ken Buck, one of the Tea Party-linked Senate candidates that year, said in reference to the former Massachusetts governor’s struggles.

While the Tea Party -- a group of especially conservative activists angered by the bailouts to the financial industry and President Barack Obama’s health care law -- helped give kindling to the GOP in 2010, its insistence on ideological fealty in Republican candidates was seen as a factor that limited their success.

Republicans were successful in retaking the House but fell short of winning the necessary seats in the Senate, where Tea Party-backed nominees in Nevada, Delaware, and Colorado lost in opportunities Republicans had hoped to gain.

(Other candidates backed by the Tea Party were able to win in states like Utah, Kentucky and Florida, however.)

NBC/Marist poll: Romney leads ahead of Wisconsin primary

But the fallout hasn’t been limited to those primaries; Boehner’s struggles to win the votes of conservative freshmen elected in 2010 are well-documented. Those freshmen have pushed their leader to hew to strictly conservative positions at major junctures in the last year and a half, fueling a perception of Republicans in Congress as an intransigent lot, while weakening the speaker’s bargaining position in fights over spending cuts and the debt ceiling.

The tug of war between ideological purity and practical politics has been on display, again, during the campaign for Republicans to pick their nominee versus Obama.

Romney has long been considered the tentative frontrunner to become the GOP’s nominee, and he appears poised now to accrue the necessary delegates to accomplish that task.

But this primary has been defined, if nothing else, than by the flailing search by conservatives to identify a more palatable alternative to Romney.

While he’s stayed steady in primary voter polls, a veritable merry-go-round of challengers -- Michele Bachmann, Rick Perry, Herman Cain, Newt Gingrich, Rick Santorum, Gingrich again, and now, Santorum again -- have overtaken him in the polls before fading.

Moreover, exit polls of the primary contests to date have borne out Romney’s struggles in winning over self-described “very conservative” primary voters -- the core of the modern Republican Party.

While Republicans of all stripes express confidence that the party will rally around the eventual nominee, the conservative wing of the party has been nothing less than dogged in its resistance to Romney.

Romney and his current main rival, Santorum, “reflect different parts of the Republican Party,” said Oklahoma Rep. Tom Cole, one of the GOP’s veteran political strategists, who has remained neutral in the primary fight.

“Both of them have proven remarkably tough and durable -- it's like watching a great bar room fight. That's the kind of punching match that we're in right now,” Cole said. “In a sense, Republican voters want to be assured that whoever emerges is tough enough to go toe to toe with the president.”

Bachmann, the Minnesota congresswoman who represented the Tea Party in her presidential bid, acknowledged last week on “Morning Joe” that the Republican Party is “factionalized” at the moment.

But some Republicans argue that Romney’s struggles were essentially avoidable, and they blamed his campaign for doing a poor job of reaching out to conservatives.

Poll: Majority of GOP says Gingrich, Paul should end campaigns

A former chairman of a major state Republican Party, who is sympathetic to Romney’s candidacy and requested to speak anonymously in order to offer more candid analysis, argued that the former Massachusetts governor’s struggles were directly related to poor outreach.

“They’ve been unwilling or unable to close the deal among conservatives,” the chairman said of the Romney campaign.

“Why don’t they send someone to Grover’s meeting in D.C.?” added that person, referring to the weekly meeting of conservative activists hosted by anti-tax advocate Grover Norquist.

The suggestion was that Romney’s campaign was basically self-involved and did little to show conservatives that Romney was one of them -- an especially curious strategy given Romney’s presidential run in 2008, which was staked on running as the conservative alternative to John McCain.

“There’s no history there; they’ve never dated,” said Craig Shirley, a Reagan biographer whose public relations firm did work for the Gingrich campaign for a stretch this primary. “It’s a little hard to ask people to marry you when you haven’t courted them first.”

The Romney campaign’s strategy, though, has sought to maintain the candidate’s viability for the general election to the best of their ability. The Romney campaign has been nothing if not careful in navigating Romney through the briar patch of conservatives’ demands on the candidate.

But the primary campaign appears to have taken its toll; a Washington Post/ABC News poll released Wednesday had Romney’s unfavorable ratings at an all-time high. Romney will no doubt pivot toward the center in the general election, but he has more ground to make up than many Republicans would like.

“The question becomes: Can the eventual Republican candidate, diminished by the primary, come back and win the election,” said Castle.

But Buck, perhaps illustrating conservatives’ ambivalence toward Romney, said it would be “fascinating” to see really how competitive Romney would be versus Obama.

“The question is, which Mitt Romney?” he asked.

Romney about to wrap it up?... NBC/Marist poll shows Romney leading Santorum in Wisconsin, 40%-33%... Demographics are destiny: Poll shows that 41% of likely GOP primary voters in Wisconsin are evangelicals, and we know what that means… Poll also finds that Obama leads in the general election… Total Recall: Wisconsin’s polarized electorate divided on recall… Ryan to endorse Romney… And Obama’s SCOTUS silence so far, but that could change today.

Sean Gardner / Reuters

Republican presidential candidate Mitt Romney addresses supporters during a "Repeal & Replace Obamacare" campaign in Metairie, Louisiana March 21, 2012.

*** Romney to wrap it up? A new NBC/Marist poll of Wisconsin, as well as Rep. Paul Ryan’s new endorsement today, suggest that Mitt Romney is on the cusp of pulling away from his Republican rivals -- and for good. In the new poll, Romney leads Rick Santorum by seven percentage points among likely GOP primary voters, 40%-33%, with Ron Paul getting 11% and Newt Gingrich 8%. And when is a seven-point lead a potential blowout? When demographics have been destiny in this GOP presidential contest. So far, Romney has won in every contest where evangelical voters have accounted for less than 50% of the electorate, and he has lost in every contest where that number has been higher than 50%. The evangelical percentage among likely Wisconsin GOP primary voters, according to the NBC/Marist poll: 41%.

SLIDESHOWS: Mitt Romney | Rick Santorum

*** Demographics are destiny: Indeed, the Wisconsin race follows a familiar pattern: Romney holds the advantage over Santorum among liberal and moderate Republicans (43%-24%), conservatives (42%-33%), non-Tea Party supporters (42%-31%), and those who earn $75,000 or more annually (47%-32%). Meanwhile, Santorum leads among very conservative primary voters (42%-33%), strong Tea Party supporters (40%-32%), and evangelical Christians (40%-29%). But look at some of Santorum’s leads among “very conservative” and among “strong” Tea Party -- they aren’t blowouts. Another bad sign for him.

*** Obama leads in the general: Looking ahead to the general election, the NBC/Marist survey shows President Obama holding a sizable advantage over his Republican opposition in Wisconsin, which he carried in 2008 but where Republicans made big gains in the 2010 midterms. Obama leads Romney in Wisconsin among registered voters, 52%-35%, with 13% undecided. And he edges Santorum, 51%-38%, with 11% undecided. The poll suggests, however, that both Romney and Santorum would have room to grow in the general election, given that a LARGE portion of the undecided vote here leans Republican. The Obama number basically matches his job-approval rating (which is 50%). What we’re learning is that the GOP-leaning voters haven’t yet bought into the GOP candidates and some are simply sitting in the “undecided’ column; keep that in mind in general these days. Benefiting Obama is growing optimism about the state of the economy (52% believe the worst is behind them), as well as a more negative perception of the Republican Party (48% say the Democratic Party does a better job in appealing to those who aren’t hard-core supporters, while just 32% say that about the GOP).

Slideshow: Obama's 4th year in office

*** Wisconsin’s polarized electorate: As for this summer’s recall contest of Republican Gov. Scott Walker, it’s looking like a coin flip: 46 % of Wisconsin voters say they will support him in that race, while 48% indicate they’ll vote for the eventual Democratic candidate who will face off against the incumbent governor. (The potential good news for Walker here: He’s down two points to a generic candidate, not one that Republicans will be able to define.) Moreover, Walker’s approval rating in the state is 48%-48% -- yet another sign of how polarized the Wisconsin electorate is.  And get this: A majority of likely Republican voters say they’re following the recall more closely than the GOP presidential primary race, 51% to 37%. Yesterday, the state determined that there are more than 900,000 valid signatures to recall Walker, and the Wisconsin Government Accountability Board is supposed to schedule the recall election today -- with primaries expected to occur on May 8 and the general on June 5. By the way, talking to strategists on both sides of the aisle about what impact the recall will have on November is this universal belief that the party that “loses” the recall will find its base a tad less enthusiastic. For Republicans, it means that a loss would almost certainly concede the state to the Democrats. For Democrats, a recall loss almost certainly means this state will be more like 2004 than 2008.

*** Ryan to endorse Romney: On FOX this morning, Ryan announced his endorsement of Romney, saying that the former Massachusetts governor "is the best person to be president" and "best person to beat" President Obama. "Mitt Romney is clearly that person," he added. Ryan also said he "spent a good deal of time with Romney" and "I am convinced Mitt Romney has the skills, principle, courage, and tenacity to do what it takes to get America back on track." And he stressed that the "primary could enter a phase when it becomes counterproductive if this drags on much longer." While Ryan held an official role with the RNC -- as head of the committee’s presidential trust -- that work is now completed, leaving Ryan free to endorse (as other RNC members and members of Congress have done).

*** On the trail, per NBC’s Adam Perez: All the activity is in Wisconsin: Santorum holds rallies in Hudson, Eau Claire, and Chippewa Falls, and he hits a fish fry and bowls in Weston… Romney stumps in Appleton and Milwaukee… And Gingrich hosts a rally in Green Bay.

*** Obama’s SCOTUS silence (so far): Well, we found out how President Obama is reacting to the three days of Supreme Court oral arguments on the landmark health-care law: with silence so far. Yesterday, in remarks from the White House on legislation to end federal subsidies to the oil industry, Obama didn’t once mention the oral arguments, which suggested that the individual mandate -- and possibly entire law -- could be in trouble. But could he say something today? The president attends a combined four fundraisers today in Vermont and Maine, and it’s possible he says something about the matter to his donors. So don’t write this up as another fundraising day. We could have some news.

Countdown to DC, Maryland, Wisconsin primaries: 4 days
Countdown to Election Day: 221 days

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FAIRFIELD, Calif. -- Rick Santorum delivered what was billed as a major foreign policy speech at One Jelly Belly Lane in his latest in a series of attempts to invoke images of conservative icon Ronald Reagan.

Speaking to a crowd gathered at Jelly Belly Candy Company here, the candy manufacturers who produced Reagan's beloved jelly beans, Santorum's policy address was part homage to the former president and part blazing critique of his chief rival for the GOP nomination, Mitt Romney.

A picture of Reagan's face made out of jelly beans hung outside on the room where the former Pennsylvania senator told supporters the spirit of the Great Communicator had been lost.  Santorum was not shy about citing Romney as an example of a politician who does not fit the Reagan mold.  Santorum said Romney's inconsistencies on issues like gay marriage and abortion rights.

"We as conservatives need to stand up and fight for a candidate that can win this general election, who stands solidly, firmly on the 3 legs of the stool that brought the Reagan coalition together," Santorum said, referring to Reagan's belief in free enterprise, strong national defense, and conservative social values.

But it is an ad in Wisconsin which Santorum says paints him as an abortion rights advocate that GOP hopeful seemed particularly bothered by.

"I find it sort of remarkable that Gov. Romney is out running ads in Wisconsin right now basically saying I'm not pro-life," Santorum said, following with a list of the anti-abortion rights legislation he help push in Congress.  "To suggest somehow or another that I am not pro-life, again, is a disingenuous game that is played by politicians who seek power instead of trying to be truthful to the American public," he said.

Santorum laid out a national security platform based in strengthening the U.S. relationship with its allies and holding other countries accountable, two things he criticized Obama for failing to have done.

"If you are a foe of the United States, and you do not respect the United States and our security interests, you will learn to fear the United States and your security interests," he said to applause.  "Of all of the failings of this president, perhaps the greatest is on national security.  And folks that’s saying something."

Visiting California meant a break from campaigning in Wisconsin, where polls showed Santorum struggling to keep pace with Romney.  And yesterday, more bad news as Sen. Marco Rubio (R-FL) gave his much anticipated endorsement to Romney.

"If an endorsement hurt me, I wouldn't be here," Santorum said while greeting voters after the event.

The candy company was Santorum's only campaign event in the Golden State, which holds its primary June 5.  He spent the earlier part of the day fundraising in the Los Angeles area.  And despite their late primary, the GOP hopeful seemed confident the state would be important this cycle.

"California doesn't get a chance very much to play in presidential politics, of late," he said.  "But you will in this presidential primary."

Upcoming Wisconsin primary is shaping up to be Santorum’s last chance…. White House more optimistic about its chances with the Supreme Court (at least compared with yesterday)… Romney’s dog-bites-man endorsements… Newt tarnishing his legacy?… So much for Simpson-Bowles’ popularity… And Dems lead OH and FL Senate contests, per new polls.

Scott Olson / Getty Images

Republican presidential candidate and former Sen. Rick Santorum, R-Pa., discusses his plan for free-market health care solutions during a campaign stop at the MacDonald and Owens Lumber Company on March 28, 2012 in Sparta, Wisconsin.

*** Santorum’s last chance (really, this is it): With Mitt Romney holding a sizable delegate lead and with more prominent Republicans (George H.W. Bush and Marco Rubio) formally endorsing the former Massachusetts governor, Tuesday’s GOP primary in Wisconsin is shaping up to be Rick Santorum’s last chance -- in math and perception. If Romney wins Wisconsin, Santorum can’t stop him from getting to the magic number of 1,114 delegates, according to our math. When we crunched the numbers showing that Romney would fall about 50 delegates short of the magic number, that ASSUMED Santorum would win Wisconsin, as well as pick up more delegates than he did in Louisiana. When it comes to perception, Wisconsin is Santorum’s final opportunity to convince Republicans that this race isn’t over, and a win in the Badger State would do the trick. Can Santorum pull off a win on Tuesday? Well, we’ll have a new NBC/Marist poll on the race tomorrow morning that could answer that question.

*** A more optimistic White House (at least compared with yesterday): Believe it or not, the White House feels better this morning about its prospects with the Supreme Court’s consideration of the health-care law than it did yesterday morning. First, the administration thinks it’s clear that a majority of the justices are against severability (that the individual mandate can be separated from the rest of the law), and they believe that could help them win over Justice Kennedy, who might be concerned about the Supreme Court striking down the whole thing. Second, the legal-eagle watchers believe that Chief Justice Roberts is still in play, and he might decide to write the majority opinion to ensure that the mandate doesn’t serve as a precedent for future regulations of commercial inactivity.

*** I will survive, hey, hey: And third, Team Obama has convinced itself that it could survive the Supreme Court striking down the law. Make no mistake: If the court does that, President Obama and his standing would take a serious hit. But they think it would only be a week or 10 days of bad press; they contend the economy and other issues would eventually overtake the court news. Also, they believe a decision to strike down the law would be done along partisan lines (5-4), and under that scenario, it politicizes the decision in a way that fires up their base and potentially blunts some of the impact with indies. Finally, Team Obama believes the biggest reason they can politically survive the SCOTUS overturning the president’s signature bill: They would probably be facing an opponent who is uniquely UNABLE to take advantage of the situation because he championed an individual mandate in Massachusetts. All that said, the White House is clearly in a tougher position than it thought before this week’s oral arguments began.

*** The dog-bites-man endorsements: Turning back to the GOP presidential race, Romney last night picked up the endorsement of GOP Sen. Marco Rubio. And this afternoon in Houston, at 5:50 pm ET, he’ll receive former President George H.W. Bush’s formal backing. Yet both endorsements are of the dog-bite-man variety: Bush 41 had already said -- in Dec. 2011 -- he was supporting Romney, and his wife Barbara has appeared in robo-calls for the campaign. As for Rubio, did anyone think he was going to endorse Santorum or Gingrich? What’s more, Rubio’s endorsement appeared to be more of an attempt to end the GOP primary battle than an affectionate embrace of Romney. "I don't have a problem with primaries, but I think we're at a stage now where at least two of the candidates have admitted that the only way to get the nomination is to have a floor fight at the convention," Rubio said on FOX last night. "It’s increasingly clear that Mitt Romney’s going to be the Republican nominee,” he said, adding: “We’ve got to come together behind who I think has earned this nomination and that’s Mitt Romney.”

*** Newt tarnishing his legacy? Politico writes that Newt Gingrich is only tarnishing his legacy the longer he stays in the GOP race. “Instead of bowing out after a string of losses, the former House speaker has decided to cap off a historic career by spending the final weeks of the campaign in a sort of political purgatory — he’ll remain in the race but as something less than a full-fledged candidate.” And get this: Gingrich Super PAC benefactor Sheldon Adelson has said that Gingrich is “at the end of his line.”

*** On the trail, per NBC’s Adam Perez: As mentioned above, Romney heads to Houston, TX to receive the endorsement of former President George H.W. Bush… Santorum is out in California, where he delivers remarks on foreign policy in Fairfield… Paul stumps in Wisconsin, holding a town hall meeting in Madison… And Gingrich is also in the Badger State, where he campaigns in Milwaukee.

*** So much for Simpson-Bowles’ popularity: Last night, the House defeated -- by a 38-382 vote -- a budget amendment on the bipartisan Simpson-Bowles recommendations. That just shows that the only way members of Congress would accept tax increases and entitlement cuts and reforms is by both Democrats and Republicans holding hands and jumping off the cliff together. What was more cynically sad were the statements of praise from folks like Paul Ryan and Steny Hoyer about the vote on Bowles-Simpson, even as both of them voted AGAINST the legislation. In addition, the House also defeated -- by a 0-414 vote -- President Obama’s budget. But a caveat here: The House didn’t vote on the president’s budget, per se; it voted on a summary of the numbers in an amendment offered by GOP Rep. Mick Mulvaney. Bottom line: It was a political gimmick.

*** Dems lead in OH and FL Senate races: Quinnipiac is out with new polls showing that Democratic Senate incumbents are leading their top GOP challengers. In Ohio, Sen. Sherrod Brown (D) is ahead of Josh Mandel (R) by 10 points among registered voters, 46%-36%. And in Florida, Sen. Bill Nelson (D) holds an eight-point advantage over Rep. Connie Mack (R), 44%-36%. What’s fueling Nelson’s lead, in particular -- female voters. Still, BOTH incumbents are under 50%, and that matters in Senate polls.

Countdown to DC, Maryland, Wisconsin primaries: 5 days
Countdown to Election Day: 222 days

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LA CROSSE, WIS. -- If it were up to Rick Santorum, the Wisconsin primary would come down to a bowling match.

For the third time in four days, the former Pennsylvania senator visited a bowling alley in the Badger State. Between frames, he casually took questions from reporters, seeming confident he could outperform rival Mitt Romney on the lanes. "I think we should maybe decide Wisconsin in a match, what do you think? Just come here, we'll say we'll put it all on the line," Santorum said.

While the GOP hopeful rolled a turkey -- three strikes in a row -- during his first bowling alley campaign stop, on Wednesday the magic was gone. After seven frames, his score sat at a measly 88.

Afterward, he told a local reporter that the aggressive bowling schedule may be taking its toll. "I think some of the reporters accurately noted that I have dead arm a little bit. It's like everything else in the campaign. You have to fight through it. You know, you have to play through injuries and dead-arm periods and keep fighting," Santorum said.

The past 24 hours have been a mix of good and bad news for Santorum.

Newt Gingrich, who Santorum aides say has drastically cut into their vote totals,  dramatically scaled down his campaign. But the former House speaker has not dropped out of the race. And as the Wisconsin primary seems to be slipping away, new polling shows the race tightening in his home state of Pennsylvania.

 "I think we'll do well here. The question is how well," Santorum said in response to a question about the importance of Wisconsin.

Advisers to the campaign have acknowledged April will be a tough month.  A spread-out calendar of primary states unfavorable to Santorum will only make it more difficult for him to remain relevant as a top contender to front-runner Mitt Romney.  Internally, the campaign feels that slogging through April can get them to May, where winning delegate-rich Texas can get them back in the conversation.

But the Keystone State's April 24 primary could prove problematic for the southwest Pennsylvanian. An oft-repeated argument on the campaign trail has been that both Romney and Gingrich got off to strong starts in the primary by winning states near their homes. Despite his double-digit loss in the 2006 Senate race, Santorum has cited Pennsylvania as a state where he will do well.

Responding to a question about the importance of winning his home state, Santorum would only say "We have every intention of winning Pennsylvania."

The majority of Santorum's campaign will be in Wisconsin leading up to Tuesday's primary. And he's hoping to get back some of the luck he had at a bowling alley on Saturday, the day he won the Louisiana primary.

"Now it’s time for Wisconsin to do what I did the other day in Sheboygan," Santorum said at a Wednesday morning rally in Sparta, Wis.

"Not just bowl one strike, not just bowl two strikes, but to bowl three strikes in a row and knock Obama out of the game by electing Rick Santorum."

DAVENPORT, Iowa -- The folksy, shirt-sleeved assault on Mitt Romney continues.

Vice President Joe Biden, who's serving a stint as the Obama administration's top campaigner, assailed the Republican candidate again Wednesday in his third campaign speech in two weeks, this time portraying Romney as a prolific outsourcer of American jobs who is pessimistic and "out of touch" with the manufacturing sector.

"America is coming back," a jacket-less Biden declared to about 450 guests at an eastern Iowa high-tech manufacturing facility Wednesday. "It's not a political slogan. It's a reality."

Despite making a tongue-in-cheek reference to Romney's "Etch-a-Sketch" flip-flops during a speech to Florida seniors last week, today Biden labeled the president's rival-in-waiting as "remarkably consistent" but "wrong" on job creation.

"Mitt Romney has been remarkably consistent -- as an individual investor, a businessman, as governor of Massachusetts, and now as a candidate for president," he said. "Remarkably consistent. And I respectfully suggest, consistently wrong."

The vice president specifically skewered Romney's record on tax cuts and business legislation, saying policies he supported as governor and during his tenure at Bain Capital encouraged American companies to push facilities and jobs offshore.

Biden did not mention Romney's personal wealth -- thrust back into the news cycle yesterday by new details of the lavish home that the former Massachusetts governor is building in California -- but he did ridicule the president's rival for calling Obama "out of touch" when encouraging young people to pursue manufacturing jobs.

"Out of touch? Romney?" he added incredulously. "As an old friend of mine says, that's chutzpah."

While Biden has previously made specific reference to all of the Republicans still fighting in the GOP race (other than Ron Paul), he mentioned only Romney and Rick Santorum by name Wednesday, leaving Newt Gingrich completely off the list. (The campaign also distributed a four-page research document to reporters focused solely on contrasting Obama and Romney's records on manufacturing issues.)

Despite reserving most of his fire for Romney, Biden also slammed Santorum, who hopes to be competitive in the upcoming Pennsylvania primary in the manufacturing-heavy state where both Santorum and Biden have roots.

"Sen. Santorum is the only one even claiming to support manufacturing," he said. "But he voted for loopholes to send American manufacturing offshore."

Appearing at PCT Engineered Systems, a Davenport company that makes electron beam systems and employs about 70 workers, Biden offered an optimistic picture of the American economy.

"I've never been more optimistic in my life for the prospects for America," he said.

Biden's visit came on both familiar and friendly territory for the campaign's top surrogate, who visited the state of Iowa some 30 times during his own run for president in 2007. Obama beat McCain in Davenport's Scott County by a 15 point margin in the general election.

The speech was his third in a series of four campaign events. Biden previously visited Ohio and Florida to tout the administration's achievements.

DELAVAN LAKE, Wisc. -- Despite news of a dramatic cutback in Newt Gingrich's presidential campaign staff, Rick Santorum is still refusing to call for the former House Speaker to leave the race.

"I think it is time for all the Republican candidates to coalesce behind me. You know, let's just have a conservative nominee to take on Barack Obama. Until that time happens, I'm not going to call on anyone to get out," Santorum said Tuesday night.

The former Pennsylvania senator spent the day campaigning through Wisconsin.  As he greeted patrons at restaurant here during his last stop, reporters told him of the reports that Gingrich had cut a third of his paid staff, including his campaign manager.  The news was met with a wince and head shake.

"One of the things I was told very early on in presidential politics is that you run for president as long as the money hangs on," said Santorum.  "Obviously, financially, it's tough. I can certainly understand that. So, I don't know what his plans are. As I've said before, were going to run the race irrespective of who's in and who's out."

Santorum said his campaign has not reached out to Gingrich, but that they "exchanged pleasantries" when they both met with the same group of reporters in Washington, DC on Monday.

Though Santorum has continually refused to call on Gingrich to leave the race, both he and senior staffers have blamed the waning GOP candidate for cutting into his vote totals and preventing a serious challenge to frontrunner Mitt Romney. Senior strategist John  Brabender has in the past openly welcomed Gingrich to be a top voice for Santorum's campaign and has also said they would like to hire his staffers.

But even as a contender fades away, the road continues to be a tough one for Santorum.  Polls show him struggling in the Badger State, where he is being heavily outspent.

He'll spend the majority of the time between now and Tuesday's primary in Wisconsin.

A majority of Republicans said former House Speaker Newt Gingrich and Texas Rep. Ron Paul should end their presidential campaigns, according to new survey data released Tuesday.

Sixty percent of Republicans said that it's time for Gingrich to leave the race, according to a new CNN/ORC International poll. Sixty-one percent said the same for Paul.

Gingrich has struggled to win any caucuses or primaries beyond the Jan. 21 South Carolina primary and the Super Tuesday primary in Georgia, the state where he was elected as a representative to Congress. He's vowed, though, to fight on with his campaign through the August Republican convention, though the former speaker acknowledged Tuesday that his campaign's finances were tight.

Paul, despite a vaunted fundraising operation and an enthusiastic corps of volunteers, hasn't scored a single victory and has faded from the campaign trail.

By contrast, a majority of Republicans -- 59 percent -- said that Rick Santorum, the former Pennsylvania senator who's emerged as the chief conservative alternative to frontrunner Mitt Romney this primary cycle, should stay in the race.

The poll, conducted March 24-25, has a 4.5 percent margin of error for the subsample of Republicans.