Watch CNN’s coverage of the fifth Republican presidential debate live from Las Vegas on Tuesday, December 15. Coverage begins at 6 p.m. ET.Washington (CNN)Nine candidates will appear in prime-time Tuesday night for the final Republican presidential primary debate of 2015, a critical event that will help shape the contest heading into the Iowa caucuses.Businessman Donald Trump, the front-runner for the nomination, will again be center stage flanked by retired neurosurgeon Ben Carson on his right and Texas Sen. Ted Cruz on his left, CNN announced Sunday. The six remaining participants in the prime-time contest will be Florida Sen. Marco Rubio, former Florida Gov. Jeb Bush, businesswoman Carly Fiorina, New Jersey Gov. Chris Christie, Ohio Gov. John Kasich, and Kentucky Sen. Rand Paul.Four candidates — former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum, South Carolina Sen. Lindsey Graham and former New York Gov. George Pataki — will appear in the first debate on Tuesday evening.