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. “In the light of new polling released this morning and in the spirit of being as inclusive as possible, CNN has decided to include Sen. Rand Paul in the prime-time debate,” a CNN spokeswoman said. Podium order was determined by the average of the national polls from November and December. RELATED: CNN Republican presidential debate criteria announced CNN’s debate, which will be held in Las Vegas and is the fifth of the primary season, is the first to use early-state polls as a way to make the main event in prime-time. Candidates must meet one of three criteria in polls conducted between October 29 and December 13 and recognized by CNN: an average of at least 3.5% nationally; at least 4% in Iowa; or at least 4% in New Hampshire. Along with Christie, Fiorina and Kasich qualified for the primetime debate because of their New Hampshire average. CNN considered live interviewer national and state surveys by ABC News, Bloomberg News, CBS News, CNN, Fox News, Gallup, Marist University, McClatchy News Service, Monmouth News Service, NBC News, The New York Times, Pew Research Center, Quinnipiac University, Time, USA Today, The Wall Street Journal, The Washington Post, The Des Moines Register, the University of New Hampshire, WBUR and WMUR. The debate will be moderated by Wolf Blitzer, with CNN’s Chief Political Correspondent Dana Bash joining Salem Radio Network talk show host Hugh Hewitt as questioners.