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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