Republican presidential candidates former U.N. Ambassador Nikki Haley and Florida Gov. Ron DeSantis participate in the FOX Business Republican Primary Debate at the Ronald Reagan Presidential Library in September. Justin Sullivan/Getty Images hide caption
Democratic presidential candidates, Sen. Bernie Sanders (left), Sen. Amy Klobuchar and businessman Tom Steyer raise their hands during a Democratic presidential primary debate on Friday at Saint Anselm College in Manchester, N.H. Elise Amendola/AP hide caption
Democratic presidential hopefuls (from left): Sen. Cory Booker, D-N.J., former Vice President Joe Biden, and Sen. Kamala Harris, D-Calif., onstage before the July debate. Brendan Smialowski/AFP/Getty Images hide caption
Workers prepare the debate stage at the Fox Theatre in Detroit ahead of Tuesday's Democratic presidential debate. Jim Watson/AFP/Getty Images hide caption
Democratic presidential candidate Sen. Elizabeth Warren of Massachusetts addresses the Moral Action Congress of the Poor People's Campaign on June 17 in Washington, D.C. Alex Wong/Getty Images hide caption
Ukrainian presidential candidate Petro Poroshenko takes a televised blood test. Sergei Chuzavkov/SOPA Images/LightRocket via Getty Images hide caption
A worker sweeps the stage prior to the first Democratic presidential debate on April 26, 2007, in Orangeburg, S.C. The debate featured eight Democratic presidential candidates. Win McNamee/Getty Images hide caption
Akilah debate team members (from left) Phylis Kabano, Sonia Rugwiro and Mireille Umutoni prepare to compete in a debate tournament. Michael May/NPR hide caption
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
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