[LAS VEGAS] Donald Trump shook off intense criticism about his anti-Muslim comments to surge to his biggest lead yet in the Republican presidential nominations race ahead of Tuesday's debate featuring the billionaire and his rivals.
Two polls unveiled Monday and Tuesday show Mr Trump at new heights, with maverick US Senator Ted Cruz surging into second place and looking to rattle the frontrunner on the national stage.
With just seven weeks before voters in the heartland state of Iowa cast the first votes in the nominations process, Mr Trump, Mr Cruz and seven other candidates will go toe to toe in Las Vegas in the final Republican presidential debate of the year.
Verbal fireworks are expected in the showdown on CNN beginning at 0130 GMT Wednesday, especially if rivals aggressively confront the bombastic real estate tycoon over his call for a ban on Muslims entering the United States.
The debate is the first since the deadly attacks in Paris and San Bernardino, California - violence that has brought national security concerns to the fore and heightened Americans' fears about illegal immigration and Syrian refugees.
Those fears likely played prominently in recent surveys, including a Monmouth University poll released Monday showing 41 per cent of Republican voters support Mr Trump, his highest position yet in the poll.
Mr Cruz surged to 14 per cent, with 10 per cent for Senator Marco Rubio and nine per cent for retired neurosurgeon Ben Carson. All others are at three per cent or lower.
In an ABC News/Washington Post poll Tuesday, Mr Trump earned 38 per cent support among registered Republicans and GOP-leaning independents, a six-point climb from November.
Mr Cruz doubled to 15 per cent, while Mr Rubio and Mr Carson were tied at 12 per cent each.
Cruz, a first-term senator with huge backing from the ultra-conservative Tea Party movement and evangelical Christians, has emerged as Trump's rival of the moment.
"He's in a pretty good position, especially when you think of evangelical and constitutional conservative types. He's the most viable for them," Seth McKee, associate professor of political science at Texas Tech University, told AFP.
Three of the last five major Iowa polls have Mr Cruz besting Mr Trump, including a Des Moines Register survey that puts the senator from Texas 10 points ahead.
Mr Rubio, also on the rise recently, is polling third in Iowa, followed by Mr Carson, whose slide in the polls is seen by some as a major gain for Mr Cruz.
Jeb Bush, the son and brother of former presidents, is a distant fifth, his campaign spinning its wheels.
Mr Trump exuded confidence Monday night at a Las Vegas rally.
"I think we're going to win Iowa, I think we're going to win New Hampshire big," he said. "If we win Iowa, we run the table."
Mr Trump's hour-long address was interrupted several times by protesters, but Mr Trump, other than urging security to "get 'em out," appeared non-plussed.
"I don't think niceness is going to matter," he said, speaking of the needs of the US electorate.
"They want competence, they want smarts, they want toughness." Establishment candidates like Mr Bush, New Jersey Governor Chris Christie and Ohio Governor John Kasich are expected to lash out against Mr Trump in the prime-time debate, which also features business executive Carly Fiorina and Senator Rand Paul.
"This will not be like an evening in paradise for me," Mr Trump admitted.
Mr Cruz, while eager to draw a distinction between himself and Mr Trump, may be careful not to antagonise him, according to experts.
"If he needs to fight back, he will. But that's not his style," Prof McKee said.
"He might push back with a smile on his face."
Mr Rubio could take a swing at Mr Cruz. Foreign policy and national security are widely regarded as Mr Rubio's wheelhouse, and on Sunday he accused Mr Cruz of being "isolationist" and for opposing bulk phone data collection.
University of Texas at Austin professor of government Bruce Buchanan said Mr Cruz was appealing to conservatives unperturbed by his poor relations with party leadership, or his lack of experience when compared to establishment candidates.
Conservatives "put ideology above pragmatism, to a degree that some of the smart money in the party would caution against. But that's what's working right now," Mr Buchanan said.
An undercard debate featuring four lower-polling candidates - Lindsey Graham, Mike Huckabee, George Pataki and Rick Santorum - will unfold before the main event, from 2300 GMT.