Personal attacks, withering ripostes, competing plans to combat terror and a surprise declaration of party loyalty marked a Republican debate in which candidates sought to reshuffle the pack six weeks before the first contest of the 2016 presidential race.

The last, most contentious Republican debate of the year ended Tuesday night with front-runner Donald Trump reiterating his pledge to forego an independent bid for the presidency if he fails to win the nomination.

"I am totally committed to the Republican party. I feel very honored to be the front runner," he said. "I will do everything in my power to beat Hillary Clinton."

Trump, who has made that pledge once before but subsequently waffled on it, made his statement at the end of a debate in which he joined President Barack Obama and Democratic front-runner Hillary Clinton as targets of fierce attacks at a televised debate.

The fifth Republican debate marked the first time the candidates have met since two deadly terrorist attacks—in Paris on Nov. 13 and in in San Bernardino, California on Dec. 2—and it offered the starkest-yet display of the split between the party's hawks and its more libertarian-leaning candidates over American security at home and abroad.

There were sharp disagreements on immigration and refugee policy and how to combat terrorism overseas.

In one particularly sharp exchange, New Jersey Governor Chris Christie called Obama a "feckless weakling" and promised to shoot down Russian planes. "If you are in favor of World War III," retorted Senator Rand Paul of Kentucky, "you have your candidate."

The first attacks of the incendiary CNN/Facebook debate, held at the Venetian casino in Las Vegas, focused on the front-runner:  "Donald is great at the one-liners, but he is a chaos candidate and he'd be a chaos president," former Florida Governor Jeb Bush said. "He would not be the commander in chief we need to keep our country safe." Later as the two tangled over airtime, Bush snapped at Trump: "You're not going to be able to insult your way to the presidency." 

The back-and-forth between the two took at times took on a a so's-your-mother quality.

"I won't get my information from the shows. I don't know if that's Saturday morning or Sunday morning," Bush said, in an apparent suggestion that Trump has been watching too many cartoons. 

When Trump complained about CNN, suggesting that the network has asked his opponents questions that give them an opening to attack him in a quest for better ratings, Bush told him to man up.

"This is a tough business," Bush said.

"You're a tough guy, Jeb, real tough," Trump shot back, before referencing their respective standings in the polls. "Let's see, I'm at 42 and you're at 3, so, so far I'm doing better." 

But with less than two months remaining before the Feb. 1 Iowa caucuses and the Feb. 9 New Hampshire primary, other candidates quickly muscled their way into the scrum.  Two particular confrontations dominated the initial hour of the main debate: Trump versus Bush and one between two Cuban-American freshmen senators:  Ted Cruz of Texas and Marco Rubio of Florida.

But the expected confrontation between Trump and Cruz, who has overtaken the billionaire in Iowa polls, never occurred. "He has a wonderful temperament," said Trump, patting Cruz on the shoulder after shrugging off a question about why, earlier in the week, he had called the senator "a maniac."

Rubio attacked Cruz, who has been surging in recent polls, over a variety of issues, criticizing the Texan for voting against spending bills that included military funding. "You can’t carpet bomb ISIS if you don’t have planes and bombs to attack them with," he said. 

Rubio also attacked Cruz for voting also attacked the Texan's vote earlier this year in favor of a law that put restrictions on how much phone data the National Security Agency can gather without a warrant, saying that Cruz "took away a tool" that allowed law enforcement "to know who terrorists have been calling."

Cruz said Rubio had thrown "more than a few insults in this direction" in recent weeks and that he'd supported foreign policy put forward by Obama and Clinton that he argued has made the world less safe. Cruz pointed to Rubio's support of a failed bipartisan immigration bill two years ago that would have offered undocumented immigrants a path to citizenship.

"He was fighting to grant amnesty, and not to secure the border," Cruz said. "I was fighting to secure the border."

Paul, whose lagging poll numbers made his presence on the prime-time debate stage doubtful until the last minute, also attacked Rubio over the immigration. "Marco can't have it both ways," said the Kentuckian, complaining about Rubio's refusal to support restrictions on refugees. "He's the weakest of all the candidates on immigration." 

Former Hewlett Carly Fiorina knocked Cruz and Rubio as not being ready to be a commander in chief, saying the nation needs someone with executive experience and "not first-term senators who have never made an executive decision in their life."

Christie piled on the senators, sarcastically commiserating with viewers after one of their exchanges. "If your eyes are glazed over like mine, this is what it's like on the floor of U.S. Senate," he said.  

Trump called for a ban on Muslim travel to the U.S. five days after the San Bernardino killing spree, perpetrated by a married couple who were inspired by the Islamic State, investigators have found. All the other Republican candidates, with the exception of Cruz, have sharply criticized his proposal.

It ignited passionate disagreements in an earlier undercard debate, and the frontrunner's name came up within the first 10 seconds of the main debate.  Paul accused the billionaire of embracing un-American ideals, such as wanting to "turn off that Internet thing." 

Trump later defended himself, saying that the Islamic State "is using the Internet better than we use the Internet." 

"We should be using our most brilliant minds to figure out a way that ISIS cannot use the Internet," he said.

On his proposal to ban Muslim travel to the U.S. he was also unapologetic. "We've opened up a very big discussion that needed to be opened up," he said to applause from the audience.

"We need to start thinking about the needs of the American people before we go and try to solve everybody else's problems," Carson said. "The fact of the matter is the Middle East has been in turmoil for thousands of years. For us to think that we're going to go in there and fix that with a couple of little bombs and a few little declarations is relatively foolish."

In the undercard debate that took place earlier in the evening, four lower-polling candidates expressed feelings ranging from concern to outrage about the billionaire's plan to ban Muslims from traveling to the U.S. 

New York Governor George Pataki called Trump "the know-nothing candidate of the 21st century," referring to a 19th century movement that targeted Catholic immigrants. He and Senator Lindsey Graham of South Carolina questioned Trump's fitness to be the nation's commander in chief.

"Declaring war on the religion only helps ISIL," said Graham of the Islamic State. "It's the worst possible thing you can do in this war," he added, saying Trump's proposed travel ban "has made us less safe." 

Afterwards, Graham told reporters that he was so upset by the tone of some of his rivals he was nearly in tears on stage. "Some of these foreign policy discussions are hurting us," he said. 

Hours before the Republican debaters took the stage, Clinton, the Democratic presidential front-runner, delivered a national security address in which she blasted her Republican would-be rivals, taking direct aim at one of Cruz's  more colorful recent statements about how he'd handle Islamic terrorism.

"Promising to carpet bomb until the desert glows doesn't make you sound strong," said Clinton. "It makes you sound like you are in over your head."

Despite being roundly condemned by most of his Republican rivals as well as Obama, Trump's proposal on Muslim travel appears to have been a political winner: In last week, Trump has enjoyed a surge in national polls. The latest show him running 20 percentage points ahead of his next nearest rival, Cruz.


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