Republican presidential hopefuls Ted Cruz, Ben Carson, Donald Trump, Jeb Bush, and Scott Walker participate in the Republican Presidential Debate at the Ronald Reagan Presidential Library in Simi Valley, California on September 16, 2015. Republican presidential frontrunner Donald Trump stepped into a campaign hornet's nest as his rivals collectively turned their sights on the billionaire in the party's second debate of the 2016 presidential race. AFP PHOTO / FREDERIC J. BROWN (Photo credit should read FREDERIC J BROWN/AFP/Getty Images)
