Then-presidential candidate Rick Santorum speaks to reporters in the spin room Jan. 14 after the undercard portion of the Fox Business Network Republican presidential debate in South Carolina.
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Republican presidential candidate Donald Trump and Fox News Channel host and moderator Megyn Kelly during the first Republican presidential debate — the origin of their feud.
Donald Trump (left) and Ted Cruz joke about Trump's comments that Cruz was a "maniac" and didn't have the right temperament to be president. They played nice then, but will they again?
Democratic presidential candidates Bernie Sanders, Hillary Clinton and Martin O'Malley stand on the stage prior to Saturday's Democratic primary presidential debate in Des Moines, Iowa.
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Republican presidential candidates, from left, Bobby Jindal, Rick Santorum, George Pataki, and Lindsey Graham take the stage during the CNBC Republican presidential debate at the University of Colorado on Wednesday.
Mark J. Terrill/AP