SIMI VALLEY, CA - SEPTEMBER 16:  Republican presidential candidates (L-R) Rick Santorum, George Pataki, U.S. Sen. Rand Paul (R-KY), Mike Huckabee, U.S. Sen. Marco Rubio (R-FL) , U.S. Sen. Ted Cruz (R-TX),  Ben Carson, Donald Trump, Jeb Bush, Wisconsin Gov. Scott Walker, Carly Fiorina, Ohio Gov. John Kasich and New Jersey Gov. Chris Christie stand onstage during the presidential debates at the Reagan Library on September 16, 2015 in Simi Valley, California. Fifteen Republican presidential candidates are participating in the second set of Republican presidential debates.  (Photo by Sandy Huffaker/Getty Images)