Story highlights Christie was relegated to the undercard debate at the last Republican event

CNN's debate in Las Vegas is the first to use early state polls as a way to make the main event in prime-time

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.

It will be a return for Christie to the prime-time stage after failing to qualify for the Fox Business prime-time debate last month. Christie has seen a resurgence in recent weeks, particularly in New Hampshire, a key state for his campaign.

Paul, who was in danger of being removed from the main stage, was saved at the 11th hour by showing viability in Iowa in a Fox News poll released Sunday morning

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