The podiums are seen on the stage during final preparations for Saturday night's Democratic presidential debate between Sen. Bernie Sanders, I-Vt., Hillary Rodham Clinton and former Maryland Gov. Martin O'Malley, in Des Moines, Iowa. Charlie Neibergall/AP hide caption

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During the 2012 campaign cycle, CNN was among several news networks that hosted Republican debates. Now, the GOP says it doesn't want to be on either that network or NBC. Joe Raedle/Getty Images hide caption

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