Who will feature in the next GOP primary debate?

GOP front-runner Donald Trump will take center stage at the primetime Republican primary debate Tuesday in Las Vegas, according to CNN, the network hosting the Las Vegas forum.

Trump will share the debate's main stage with eight other GOP presidential candidates: retired neurosurgeon Ben Carson, Texas Sen. Ted Cruz, former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio, New Jersey Gov. Chris Christie, former tech executive Carly Fiorina, Ohio Gov. John Kasich, and Kentucky Sen. Rand Paul.

The top-tier debate will begin at 8:30 PM ET on December 15.

Since the last Republican gathering, the field for the primetime debate has widened marginally, with one candidate showing enough momentum in the polls to move up: New Jersey Gov. Chris Christie.

For the main stage, CNN allows any candidate who averages 3.5 percent in national polling (in polls from certain pollsters over a set period of time) or 4 percentage points in either Iowa or New Hampshire polling.

The participants In the undercard debate, airing at 6:00 PM ET, include former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum, South Carolina Sen. Lindsey Graham, and former New York Gov. George Pataki. Missing from the second-tier debate is Louisiana Gov. Bobby Jindal, who dropped out of the primary race shortly after the last GOP debate. Pataki, who did not register high enough in polls to feature in the previous Fox Business/Wall Street Journal debate, has taken his place.

Participation on the earlier stage only requires that a candidate appears in four of the predetermined polls at 1 percent or higher.

CNN anchor Wolf Blitzer will moderate the debate, with CNN's Dana Bash and conservative talk radio host Hugh Hewitt serving as additional panelists.

Tuesday's forum will be the fifth Republican primary debate. In contrast, Democrats, with a narrower candidate field, have only had two debates so far.