Las Vegas Debate Preview

It's debate night in Sin City. Republican presidential candidates are in Las Vegas for their last debate of the year, just seven weeks before the 2016 nominating race gets underway at the Iowa caucuses. And what unfolds on stage at the Venetian casino will have significant implications for the destiny of the GOP nomination.

In the five weeks since the last Republican presidential debate, terrorists have struck in Paris and San Bernardino, Calif., Donald J. Trump has proposed barring Muslims from coming to America, Ben Carson’s support has evaporated and Senator Ted Cruz of Texas has emerged as Mr. Trump’s stiffest competition. Senator Marco Rubio of Florida has gone on the attack against Mr. Cruz, and Gov. Chris Christie of New Jersey, who has less money than many senators up for re-election, has shown signs of life, at least in New Hampshire.