The White House announced Tuesday that, beginning this weekend, presidential limousines will bear the District of Columbia license plate that includes the phrase "Taxation Without Representation."

The license plate, created in 2000, adorns most of D.C.'s vehicles with a pithy reminder that residents of the capital city do not have voting representatives in the House or Senate. New registrants in the city now receive the tags automatically unless they opt for another type of license plate. 

 The saying has become a rally cry for proponents of D.C. statehood.

"President Obama has lived in the District now for four years, and has seen first-hand how patently unfair it is for working families in D.C. to work hard, raise children and pay taxes, without having a vote in Congress," said White House spokesman Keith Maley. "Attaching these plates to the presidential vehicles demonstrates the President's commitment to the principle of full representation for the people of the District of Columbia and his willingness to fight for voting rights, Home Rule and budget autonomy for the District."

The license plates will be affixed to presidential vehicles in time for the weekend’s inaugural festivities and remain in place for the duration of Obama's presidency. 

WASHINGTON -- Appearing at an annual gathering of conservative Christian voters, former presidential candidate Rick Santorum accused President Barack Obama of "coddling and appeasing" America's enemies and said the Obama administration is at least partially responsible for ongoing violence in post-Arab Spring nations.

"This president has to take a share of the responsibility for what the Middle East looks like today because he helped structure it," Santorum told attendees at the Values Voter Summit in Washington, D.C., adding that Obama has "turned his back" on allies like Israel and the government of Egypt.

"He has sent a very clear message to that area of the world," he said of Obama. "If you're a friend of the United States, you're on your own. If you are an enemy of the United States, let's talk."

Anti-U.S. protests rocked over 20 nations across the Middle East, Africa, and Asia this week, and four Americans were killed during an attack in Benghazi, Libya.

Republican presidential nominee Mitt Romney has slammed the Obama administration for "apologizing" for American values in its dealings with Islamic militants, a sentiment that his former rival Santorum echoed today.

"Gov. Romney boldly went out and called this administration on their policies, their weak, lead-from-behind appeasing policies against those who threaten us and our security," Santorum said. "He stood up and called them what they were."

While he fought bitterly against the now-GOP nominee in the Republican primary, the former Pennsylvania senator repeatedly praised Romney before the audience of Christian social conservatives, a group that represents the backbone of Santorum's political base.

"I'm so encouraged that Gov. Romney has embraced some of the things I campaigned upon and that you across America have encouraged me to give voice to," he said. "He's giving voice to those things because he understands who we are. Mitt Romney understands America. He understands those values. And he shares those values."

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.