Donald Trump gets advantage with crowded debate stage

When it comes to Tuesday night’s GOP presidential debates, it’s the more candidates, the merrier as far as Republican front-runner Donald Trump is concerned.

With the Feb. 1 Iowa caucuses just six weeks away, there’s a baker’s dozen of active candidates still in the race and all are expected to be on the stage for one of the two debates at the Venetian Hotel in Las Vegas.

For Trump, the businessman and former reality TV host who has held the top spot in the Republican polls almost since he announced his candidacy in June, it’s all about the numbers. His 35 percent support in the latest New York Times/CBS poll gives him a huge lead when there are a dozen other candidates splitting up the remaining 65 percent of GOP voters.

But if the field gets trimmed to two or three candidates, that 35 percent becomes a far less formidable number.

“Trump has a rock-solid 25 percent base, and there’s nothing better for him than to have more candidates visible and in the ring,” said political analyst Sherry Bebitch Jeffe of the University of Southern California. “But as people drop out, the arithmetic gets bad.”

Winnowing unlikely

Tuesday’s 5:30 p.m. main event is likely to do little to cull the GOP field. While there had been rumors that CNN, the debate’s sponsor, might tighten entry requirements to put fewer people on the main stage, that didn’t happen.

Not only will the featured debate include every candidate with an average of 3.5 percent in selected national polls since Oct. 29, but also those with support at 4 percent or better in Iowa or New Hampshire, which holds its primary Feb. 9.

Only five candidates — Trump, Texas Sen. Ted Cruz, Florida Sen. Marco Rubio, physician Ben Carson and former Florida Gov. Jeb Bush — clear that national mark, according to the RealClearPolitics average of polls.

But with the state polls added, businesswoman Carly Fiorina, Ohio Gov. John Kasich and New Jersey Gov. Chris Christie join the main event, with Kentucky Sen. Rand Paul making the main event on the basis of a 5 percent showing in a new Iowa poll and the kindness of the debate’s sponsor.

“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 Sunday.

With the bar for the second-tier debate set at an embarrassingly low 1 percent support in any combination of four national, Iowa or New Hampshire polls, the 3 p.m. event will include the foursome of former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum, South Carolina Sen. Lindsey Graham and former New York Gov. George Pataki.

After the Dec. 2 Islamic State-inspired massacre of 14 people in San Bernardino, there’s little doubt the debates will focus on national security, foreign affairs and immigration. The real question is how the candidates will respond.

Not backing down

Trump has doubled down on his already harsh stance on immigration, saying last week that noncitizen Muslims should be barred from entering the United States, whether as immigrants, tourists or visitors. While most of the other Republican candidates quickly condemned the proposal, there’s a question of how far they’ll take that disapproval in a face-to-face showdown with Trump.

“What you may see are all the candidates ganging up on Trump,” Jeffe said. But with a new NBC/Wall Street Journal poll showing that Republicans back Trump’s ban on Muslims, 42 to 36 percent, the candidates “have to decide whether they want to risk what they have.”

For presidential hopefuls mired in the single digits, though, there may be little or nothing to lose with an all-out attack on the front-runner.

“If anyone takes Trump on, it could be Christie,” Jeffe said.

While the New Jersey governor is only at 3 percent in the latest national poll, another survey has shown him running second, behind only Trump, in New Hampshire.

Christie, who styles himself as a hard-charging, crime-fighting, terrorist-chasing former U.S. attorney, has never shied away from a fight. Last week, he called Trump’s proposed Muslim ban “ridiculous,” arguing that “this is the kind of thing people say when they have no experience and no idea what they’re talking about.”

A high-profile showing in Tuesday’s debate could give Christie a boost in New Hampshire that could translate to a jump in his national numbers, Jeffe said.

“If he does well in New Hampshire, you can’t count him out,” she added.

Cruz also faces a dilemma. While polls in the past few days have shown him rocketing past Trump in Iowa and on the rise nationally, he’s also the second choice for many of Trump’s conservative, outsider-loving supporters and might not want to risk their ire by slamming their guy on Tuesday night.

That’s not a concern for Trump, who began whacking Cruz almost as soon as the latest poll numbers were reported. On “Fox News Sunday,” for example, the businessman this weekend characterized Cruz as “a bit of a maniac,” who doesn’t have the right temperament or proper judgment to be president.

Unpredictable contest

But there’s been nothing predictable about the 2016 GOP race. Wisconsin Gov. Scott Walker, an early favorite, abruptly ended his campaign when his money ran out. Carson, who was challenging for the lead last month, has quickly slipped back into the pack as Cruz has surged into second place. And Bush, the first choice of the Republican establishment, now languishes in the dreary realm of single-digit candidates.

“I’ve never seen a race this fluid,” Jeffe said.

John Wildermuth is a San Francisco Chronicle staff writer. E-mail: jwildermuth@sfchronicle.com Twitter: @jfwildermuth

GOP debates on CNN

Second-tier debate: 3 p.m.

Main debate: 5:30 p.m.