Trump on Top, Cruz on Rise as Republicans Prep for Debate

Republican presidential hopefuls square off Tuesday in their latest debate, with maverick Senator Ted Cruz -- on the rise in key early primary state Iowa -- looking to rattle frontrunner Donald Trump.

With 50 days to go before the heartland US state casts the first votes in the nominations process, Trump, 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, set to begin at 0130 GMT Wednesday, especially if rivals aggressively confront the bombastic Trump over his call for a ban on all Muslims entering the United States.

The debate is the first since the deadly terror attacks in Paris and San Bernardino, California -- acts that have brought national security concerns to the fore and heightened Americans' fears about illegal immigration, Syrian refugees and the need to tighten the country's borders.

Trump will take center stage, as he has for each of the last four debates.

But experts and recent polls agree that 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.

Cruz, whose pledge to take on Washington resonates with far-right conservatives, has won key endorsements recently including from Bob Vander Plaats, an influential Iowa evangelical, and prominent Iowa congressman Steve King.

Three of the last four major Iowa polls have Cruz besting Trump, including a Des Moines Register survey that puts the senator from Texas 10 points ahead.

Senator Marco Rubio, also on the rise recently, is polling third in Iowa, followed by retired neurosurgeon Ben Carson, whose slide in the polls is seen by some as a major gain for Cruz.

Jeb Bush, the son and brother of former presidents, is a distant fifth, his campaign failing to meet expectations.

Nationally, however, Trump is widening his lead.

A Monmouth University poll released Monday showed 41 percent of Republican voters supporting Trump for the nomination, compared with 14 percent for Cruz, 10 percent for Rubio and nine percent for Carson. All others are at three percent or lower.

Establishment candidates like Bush, New Jersey Governor Chris Christie and Ohio Governor John Kasich are expected to lash out against Trump in the prime-time debate, which will also feature business executive Carly Fiorina and Senator Rand Paul.

But Cruz, while eager to draw a distinction between himself and Trump, may be careful not to antagonize him, according to experts.

"If he needs to fight back, he will. But that's not his style," McKee said.

"He might push back with a smile on his face."

Trump has had success in pummeling rivals who go on the offensive against him, notably Bush, Kasich and Paul.

On Sunday, Trump dismissed Cruz as a "maniac" without the right temperament for the Oval Office.

Cruz declined to take the gloves off, instead tweeting a crafty response to his "friend" Trump: a clip from the 1980s movie "Flashdance" featuring the hit song "Maniac."

Rubio could take a swing at Cruz. Foreign policy and national security are widely regarded as Rubio's wheelhouse, and on Sunday, he accused Cruz of being "isolationist" and for opposing bulk phone data collection.

University of Texas at Austin professor of government Bruce Buchanan said Cruz was a "whip-smart" and disciplined candidate savvily appealing to conservatives who are unperturbed by his poor relations with the leadership in his own party, 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," Buchanan said.

With Cruz's political stock rising, nationally renowned radio talk show host Rush Limbaugh said Monday that a Cruz win in Iowa would "shake up the establishment" and "rattle them like you can't believe."

An under-card debate featuring four lower-polling candidates -- Lindsey Graham, Mike Huckabee, George Pataki and Rick Santorum -- will unfold before the main event, from 2300 GMT Tuesday.