President Obama and first lady Michelle Obama listen as a choir performs during the groundbreaking ceremony for the Smithsonian National Museum of African American History and Culture in Washington, D.C., on Wednesday. Saul Loeb/AFP/Getty Images hide caption

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Rick Santorum gestures toward Republican rival Mitt Romney during the South Carolina GOP presidential debate in Myrtle Beach on Jan. 16. Charles Dharapak /AFP/Getty Images hide caption

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Republican presidential candidate Mitt Romney speaks to supporters at a rally in Denver on Tuesday. Marc Piscotty/Getty Images hide caption

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Republican presidential candidate Mitt Romney speaks during a campaign rally Wednesday at Brady Industries in Las Vegas. Ethan Miller/Getty Images hide caption

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From left, former Pennsylvania Sen. Rick Santorum, former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich and Texas Rep. Ron Paul, at a debate Thursday in Charleston, S.C. Win McNamee/Getty Images hide caption

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Mitt Romney and Newt Gingrich face off at the ABC News GOP Presidential Debate on Dec. 10. Kevork Djansezian/Getty Images hide caption

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Republican presidential candidates Mitt Romney (left) and Newt Gingrich shake hands after a Republican presidential debate in Tampa, Fla. Mike Carlson/AP hide caption

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President Obama received a warm welcome at Scranton High School in Scranton, Pa., Wednesday. A surge in Hispanic voters in that state could make his chances of winning it a little more likely. Carolyn Kaster/AP hide caption

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Republican presidential candidate Mitt Romney speaks during a town hall event in Peterborough, N.H., on Saturday. Michael Dwyer/AP hide caption

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Ross Perot, shown on a video screen, addresses the Reform Party's national convention in July 1999 in Dearborn, Mich. The billionaire founder of the Reform Party, Perot ran for president as a third-party candidate in both 1992 and 1996. Jeff Kowalsky/AFP/Getty Images hide caption

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President Obama greets diners in Los Angeles last month. He faces long odds in his quest for re-election. Among them: unemployment, eroding support among independent voters and approval ratings that are well below those of previous presidents who won a second term. Jewel Samad /AFP/Getty Images hide caption

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A sign at an Occupy D.C. protest reads "Fed Owns Obama." The president has so far had the worst of both worlds, with much of Wall Street convinced he's anti-business, and the protesters convinced he's in bed with the banks.

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A new ad from Herman Cain features his campaign manager, Mark Block, taking a drag from a cigarette.

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Former Massachusetts Gov. Mitt Romney (left) and Texas Gov. Rick Perry got into a heated exchange about immigration during Tuesday's GOP presidential debate in Las Vegas.

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Republican presidential candidate Herman Cain participates in a presidential debate at Dartmouth College in Hanover, N.H., on Tuesday.

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