Although the last Republican presidential debate in Milwaukee was only about a month ago, the world and debate landscape has dramatically changed since early November.  The attacks in Paris and San Bernardino will serve as a towering backdrop to tonight's debate at The Venetian in Las Vegas.  While debate subject matter will be shifting to the issues of terrorism and national security, the lineups and podium order of the undercard and main events will also be fresh and new.  Donald TrumpDonald TrumpConway: Trump doesn't think he's lying on voter fraud, wiretap claims 'The Simpsons' turned down Trump guest appearance on show: producer GOP consultant: Kid Rock would be 'prohibitive favorite' if he enters Michigan Senate race MORE continues to maintain a commanding lead in all national polls, but Sen. Ted CruzTed CruzGOP wrestles with soaring deductibles in healthcare bill Cruz: Tax reform chances ‘drop significantly’ if healthcare fails Ex-CBO directors defend against GOP attacks on ObamaCare analysis MORE (R-Texas) now enjoys a sizeable lead in the state of Iowa according to the latest Des Moines Register/Bloomberg Politics poll.  Aided by the recent endorsement of the Union Leader, Gov. Chris Christie (R-N.J.) has significantly improved his polling in New Hampshire and will be on main stage this time.   The fireworks tonight will emanate from the trio of Trump, Cruz, and Sen. Marco RubioMarco RubioBush ethics lawyer: Congress must tell Trump not to fire Mueller The private alternative to the National Flood Insurance Program  Cruz offers bill to weaken labor board's power MORE (R-Fla.).  Their personalities and bluster should provide for an evening with more entertainment than any Las Vegas show.

Fox News' Brent Baier began the inaugural Republican debate in Cleveland with a hand-raising question regarding support of the eventual nominee and third party candidacies.  Donald Trump quickly found himself isolated and defensive against the other candidates on the stage.  A repeat of this scenario is possible Tuesday over his proposal to temporarily ban Muslims from entering the United States.  All of the other candidates have rebuked this idea, but recent polling from Rasmussen Reports finds a majority of likely Republican voters back Trump's proposal and some of his polling has increased since the statement was released.   This issue will likely dominate the early portion of the debate and it will be interesting to see whether audience reaction is consistent with polling data.

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The detente between Trump and Cruz was finally broken last week.  Their positioning next to each other on stage means CNN moderators will do everything in their power to ensure combative back and forth exchanges between the two frontrunner candidates.  Cruz's performance in the Denver debate was universally lauded, but largely comprised of attacking the CNBC moderators and media in general.  While Cruz is excellent at working a room and audience, it's unclear how he will fare on stage next to Trump with heightened expectations because of his frontrunner status in Iowa.  A debate that is heavily focused on terrorism and national security does not necessarily play to Cruz's strengths, especially given his Senate votes on defense spending and intelligence gathering.  Trump's attacks on Cruz will likely focus on temperament, negotiating style, and ethanol subsidies. 

Christie received rave reviews for his undercard debate performance in Milwaukee.  He's been promoted to the main stage on Tuesday and will have to contend with higher expectations and a target on his back because of strong polling numbers in New Hampshire.  Carly Fiorina hasn't been able to fully replicate her debate success during the undercard debate in Cleveland and Christie's campaign is surely cognizant of this and has likely developed a game plan accordingly.  Christie is one of the few candidates on stage with the personality and skill set to successfully win a debate exchange with Donald Trump.  Areas of disagreement that have emerged on the campaign trail recently that will likely come up during the debate include Bridgegate, Christie's support for President Obama after Hurricane Sandy, and Trump's contention that thousands of Muslims in New Jersey cheered following the attacks on September 11th.  Trump has demonstrated in previous debate exchanges with Sen. Rand PaulRand PaulSenate healthcare bill appears headed for failure Talk of Trump pardons reverberates on Sunday shows Paul says president likely has authority to pardon himself MORE (R-Ky.) and Gov. John Kasich (R-Ohio) that he's an excellent counter puncher.  If Christie chooses to go on the offensive against Trump, he'll have to plan several moves ahead so he doesn't get ambushed like Jeb Bush during his attack against Rubio in Denver.

Tonight's debate in Las Vegas  will be the last time Republican candidates get to make favorable impressions on voters before the holiday season.  The stakes are extremely high and several candidates will be gambling their political futures on decisions and strategies made in real time during the two-hour affair.  The recent events in Paris and San Bernardino will radically alter the tenor of the debate and the nine candidates must rise to the occasion and appropriately adjust their strategies.   The trio of Trump, Cruz and Christie are likely to be the stars of the show in Las Vegas and expect them to produce a tremendous amount of fireworks that could fundamentally impact the trajectory of the race before the first ballots are cast in early 2016.

Kall is director of Debate at the University of Michigan.