LAS VEGAS, NV - OCTOBER 13:  (L-R) Democratic presidential candidates Sen. Bernie Sanders (I-VT) Hillary Clinton and Martin O'Malley walk on the stage at the end of a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate.  (Photo by Joe Raedle/Getty Images)
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