LAS VEGAS, NV - OCTOBER 13:  Democratic presidential candidates (L-R) Sen. Bernie Sanders (I-VT), Hillary Clinton and Martin O'Malley take the stage for a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. The candidates participated in the party's first presidential debate with Jim Webb and Lincoln Chafee.  (Photo by Alex Wong/Getty Images)