Former House Speaker Newt Gingrich participates in the Republican presidential candidate debate in Charleston, S.C., Thursday. David Goldman/AP hide caption

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GOP presidential hopeful Newt Gingrich addresses the South Carolina Chamber of Commerce on Tuesday in Columbia, S.C. The state holds its primary on Saturday. Paul J. Richards/AFP/Getty Images hide caption

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Republican presidential candidate former U.S. Sen. Rick Santorum speaks to supporters after announcing that he was endorsed Saturday by the evangelical Christian leaders group. Mark Wilson/Getty Images hide caption

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Former Massachusetts Governor Mitt Romney greets supporters during a campaign stop at Cherokee Trikes and More in Greer, S.C. on Thursday. BRIAN SNYDER/Reuters /Landov hide caption

itoggle caption BRIAN SNYDER/Reuters /Landov