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.

ANNAPOLIS, MD -- While vowing to stay in the race until the Republican convention, Newt Gingrich admitted Tuesday morning that his campaign “money is very tight” and they are going to have to run a tight ship.

“I have the money to keep going,” Gingrich told reporters outside the Maryland statehouse. “We’re working through what it is going to take to get” to the convention.

The former House speaker, who also visited a famous local diner -- Chick and Ruth’s -- would not say whether he would need to lay off or cut staffers' pay in order to make it to Tampa in August. He did, however, turn down the notion that he cancelled his trip to North Carolina Wednesday for financial reasons.

“The only reason we cancelled North Carolina was to do things in Washington. We had an opportunity to do a couple things in Washington tomorrow and the Washington primary’s next Tuesday, and so that’s why we stayed in Washington,” he said.

The Gingrich campaign also began charging attendees at public events $50 to take a formal picture with the speaker that would be posted on their website -- something that only happened at fundraisers in the past.

The basic message being pushed today while campaigning in Maryland is that the race is far from over in Gingrich’s eyes. Maryland holds its primary on April 3.

“Gov. Romney is the frontrunner but is a long way from a majority,” Gingrich told reporters and promised to throw his support behind the former Massachusetts Governor if he becomes the party’s nominee.

“If he does get -- by the time Utah votes on June 26 -- a majority, I will support him and will be delighted to do everything I can to help defeat Barack Obama,” he said. “If, however, we get to June 26 and Gov. Romney doesn’t have a majority, I think we'll have one of the most interesting conventions in American history.”

The speaker heads to Maryland’s Eastern Shore Tuesday afternoon to speak to students at Salisbury University.

Republican presidential candidate and former Senator Rick Santorum holds up an Etch-a-sketch while addressing supporters at a "Get Out The Vote" rally in Mandeville, La., March 21, 2012.

ARBUTUS, MD -- Mitt Romney said he plans to run on the same issues in the general election as he has in the primary in response to a top aide's comment likening Romney's pivot to the general election to an Etch A Sketch.

Romney acted to hastily control the damage resulting from comments by adviser Eric Fehrnstrom on CNN, which prompted a day's worth of attacks from Democrats, as well as Romney's Republican rivals.

Romney told reporters following his lone event today that while his campaign will change organization, the issues on which he'll run "will be exactly the same."

"I'm running as a conservative Republican," he said. "I'll be running as a conservative Republican nominee."

The comments gave Rick Santorum and Newt Gingrich a new weapon to use against Romney, figuratively and literally illustrating their case that the former Massachusetts governor is only a conservative of political convenience.

The two men, who lag behind Romney in the delegate count, jumped at the opportunity to attack Romney after a senior adviser, Eric Fehrnstrom, this morning compared moving into the general election campaign to the children’s toy this morning, saying, “you can kind of shake it up and restart all of over again.”

Both Gingrich and Santorum brought small Etch A Sketch toys to their afternoon events in the state of Louisiana. 

“We're not looking for someone who's the Etch A Sketch candidate,” Santorum said after pulling out the toy during his event in Mandeville. “We're looking for someone who writes what they believe in in stone and stands true to what they say."

Santorum even told the crowd it was “the first of what I’m going to now call my ‘Etch A Sketch Tour of America.'"

“Given everybody's fears about Gov. Romney's flip flops, to have his communications director say publicly to all of us, if we're dumb enough to nominate him we should expect by the acceptance speech he'll move back to the left, triggers everything we should worry about,” Gingrich said as he began his town hall in Lake Charles, where he appeared holding the toy. "I think having an Etch A Sketch as your campaign model, raises every doubt about where we're going."

The former House speaker handed the popular childhood toy to a little girl sitting in the front row of the Harlequin Steaks and Seafood restaurant and joked, “You can now be a presidential candidate.” (Gingrich went on and autographed the toy for her after the event.)

Santorum said he purchased his Etch A Sketch at a Toys R Us store “down the way” while the Gingrich campaign simply said they bought the “Cars” themed toy today.

But the two candidates themselves were not alone in their purchases.

More than 2,000 miles away outside Romney's Arbutus event, Santorum’s press secretary was passing out mini Etch A Sketches in the parking lot.

Holding the one remaining toy she had yet to distribute, Alice Stewart told reporters this “gaffe” from a top Romney advisor “confirms what a lot of conservative have been afraid of.”

“The campaign acknowledged that his [Romney’s] conservative credentials can come and go with the climate, just like an Etch A Sketch, and we can’t have that,” Stewart said.

Romney had initially refused to address Fehrnstrom’s Etch A Sketch comments while asked several times on the ropeline following his event in Maryland.

“I’m not doing a press conference right now, OK?” Romney told reporters.

One group that does seem happy with all the buzz of the children’s toy today is the Ohio Art Company, the Etch A Sketch manufacturer.

"Happy to see Etch A Sketch, an American classic toy, is DRAWING attention with political candidates as a cultural icon and important piece of our society," said Nicole Gresh, spokeswoman for the manufacturer. "A profound toy, highly recognized and loved by all, is now SHAKING up the national debate. Nothing is as quintessentially American as Etch A Sketch and a good old fashion political debate.”

Alex Moe reported from Lake Charles, LA. Jamie Novogrod reported from Mandeville, LA.