Rep. Ron Paul Rep. Ron Paul

Texas Rep. Ron Paul (right) talks with the his presidential campaign manager, Jesse Benton, backstage at the Republican Party's Iowa straw poll last August. Charles Dharapak/AP hide caption

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Charles Dharapak/AP

Ten states hold GOP nominating contests on March 6. Here a voter heads to a polling station Tuesday morning in Cambridge, Mass., where former Gov. Mitt Romney is expected to win his home state. Emmanuel Dunand /AFP/Getty Images hide caption

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Emmanuel Dunand /AFP/Getty Images

Former Massachusetts Gov. Mitt Romney waves to the crowd as he is introduced at the start of Wednesday night's Republican presidential debate in Mesa, Ariz. Ross D. Franklin/AP hide caption

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Ross D. Franklin/AP

Republican presidential hopeful and former U.S. Sen. Rick Santorum speaks to supporters, flanked by his daughter, Elizabeth (left), and wife, Karen. Whitney Curtis/Getty Images hide caption

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Whitney Curtis/Getty Images