A lot has changed since last month’s Republican presidential debate in Milwaukee. Outsiders Ben Carson and Carly Fiorina have sunk in the polls, while Sens. Ted Cruz and Marco Rubio have risen on renewed national security concerns after two bloody terror attacks — one in Paris, another in San Benardino, Calif.

But as the Republican candidates converge on a Las Vegas stage Tuesday for the fifth GOP debate, the one constant in the race remains the front-runner status of Donald Trump, the pugnacious billionaire who has maintained a stunning lead over the field in national polls.

The latest Real Clear Politics averages have Cruz, Rubio and Carson each polling at around 15 percent — about half the 30 percent of Republicans backing Trump, who saw his numbers jump again after controversial comments last week about a “total and complete” shutdown on Muslim travel to the United States.

In Tuesday’s CNN-moderated debate, Trump is likely to defend the Muslim comments, as he did again Sunday, while also looking to reclaim momentum in Iowa, where Cruz is surging.

In an interview Sunday with Fox, Trump brushed aside criticism of the proposed travel ban, widely panned by leaders across the political spectrum, including Republicans like House Speaker Paul D. Ryan and presidential rivals former Florida Gov. Jeb Bush and South Carolina Sen. Lindsey Graham.

Trump said on “Fox News Sunday” he sees the ban as a temporary solution “until we get our hands around this problem.”

“There’s a group of people who are very sick. We have to figure out the answer. The Muslims can help us figure out the answer,” he said.

After a Des Moines Register/Bloomberg Politics Iowa Poll released Saturday showed Cruz with a 10-point lead in Iowa, 31 percent to 21, and a Fox News poll released Sunday had the Texan up 32 percent to 25 in the state, Trump ramped up his criticism of Cruz.

“The way he’s dealt with the Senate — where he goes in frankly like a bit of a maniac — you never get things done that way,” the GOP front-runner said on Fox. “You can’t walk into the Senate and scream and call people liars and not be able to cajole and get along with people. He’ll never get anything done.”

Trump began targeting Cruz after The New York Times last week reported Cruz questioned the presidential qualifications of Trump and Carson in a closed-door session with campaign donors.

“Well look he’s from Texas — to the best of my knowledge, there’s a lot of oil in Texas, right? So, he gets a lot of money from the oil companies, and he’s against ethanol,” Trump told an ethanol-friendly crowd in Iowa last week.

In an audiotape of his comments at the fundraiser, obtained by the Times, Cruz tells supporters the terror attacks had made it more difficult for Trump to become the GOP nominee.

“You look at Paris, you look at San Bernardino, it’s given a seriousness to this race,” Cruz said.

The Texas senator, who has avoided going head-to-head with both Trump and Carson in hopes of eventually claiming their supporters, goes on to suggest voters will eventually reject both men out of concerns for national security.

“Who am I comfortable having their finger on the button? Now that’s a question of strength, but it’s also a question of judgment. And I think that is a question that is a challenging question for both of them,” he said on the tape.

On Twitter, Trump predicted it would be “easy” to beat Cruz.

While Trump was unloading on Cruz, the Texan was sticking to his strategy of trying to play nice, calling Trump a “friend,” and tweeting a link to the video for “Maniac,” the theme to the 1983 film “Flashdance.” Asked about the Trump Muslim ban last week, Cruz said: “I disagree with that proposal,” while adding, “I like Donald Trump.”

Rubio, also rising in the Real Clear Politics averages, took a harder line on Trump, telling “Meet the Press” on Sunday that the Musljm ban was “offensive and outlandish.”

Cruz, Rubio and Trump will be joined on the Las Vegas stage at 8:30 p.m. Eastern by six other “first-tier” candidates: Carson, Bush, Fiorina, New Jersey Gov. Chris Christie, Ohio Gov. John Kasich, and Kentucky Sen. Rand Paul.

CNN will hold an undercard debate at 6 p.m. for the four other GOP candidates: Graham, former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum and former New York Gov. George Pataki.