GOP candidates just brawled in their feistiest and most substantive debate yet

Within minutes, it was clear that the fifth Republican presidential debate would be perhaps the most contentious yet.

The Tuesday-night CNN debate’s first question focused on Donald Trump’s plan to temporarily ban Muslims from coming to the US, a proposal for which he would face heat all night.

Former Florida Gov. Jeb Bush (R), as he did repeatedly throughout the event, promptly went after Trump.

“Donald is great at the one-liners, but he’s a chaos candidate and he’d be a chaos president,” Bush said. “He would not be the commander in chief we need to keep our country safe.”

Trump shot back, saying Bush’s attacks on him were inauthentic, politically calculated barbs.

“Jeb doesn’t really believe I’m unhinged. He said that very simply because he has failed in this campaign,” Trump said. “It’s been a total disaster, nobody cares, and frankly I’m the most solid person up here.”

It continued like this for most of the night. The fifth and final Republican presidential debate of 2015 proved one of the most spirited, yet also perhaps the most substantive, of the affairs thus far. Candidates jostled in sharp exchanges over national security and foreign policy, trading personal insults and barbs along the way.

The debate largely focused on matters of national security and terrorism, weeks after the terror attacks in San Bernardino, California, and on the same day as a “credible” threat — which seemingly turned out to be a hoax — forced the closure of the nation’s second-largest school district.

Bush and Trump repeatedly clashed throughout the debate over national-security issues, as Bush provoked the real-estate mogul by attacking his credibility.

In a heated exchange over immigration and Trump’s suggestion that the US should go after family members of terrorists in addition to the extremists themselves, Bush slammed Trump. He referenced Trump’s claim that he gets much of his foreign-policy information from “the shows.” He suggested that Trump was actually watching cartoons.

“I won’t get my information from ‘the shows.’ I don’t know if that’s Saturday morning or Sunday morning. I don’t know which one,” Bush quipped.

The exchange quickly devolved into personal attacks.

“I know that you’re trying to build up your energy, Jeb, but it’s not working,” Trump said.

“Donald, you’re not going to be able to insult your way to the presidency,” Bush responded.

The two candidates devolved again into personal attacks several minutes later, when Bush asserted that Trump’s complaints about CNN demonstrated that that billionaire businessman was thin-skinned.

“Look, the simple fact is if you think this is tough and you’re not being treated fairly, imagine what it’s going to be like dealing with Putin or dealing with President Xi or dealing with the Islamic terrorism that exists,” Bush said, referring to the presidents of Russia and China. “This is a tough business, to run for president.”

Trump shot back.

“Oh, yeah. Oh, yeah, you’re a tough guy, Jeb,” Trump replied to laughter. “Real tough.”

Bush and Trump were far from the only candidates who clashed.

Sen. Ted Cruz (R-Texas) and Sen. Marco Rubio (R-Florida), who have each had the other in their sights over the past month as they have surged in polls, sparred repeatedly over national security and immigration.

Rubio specifically dinged Cruz for his support for the USA Freedom Act, which curbed the National Security Agency’s mass telephone-metadata surveillance program exposed in 2013 by former NSA contractor Edward Snowden.

“This bill did, however, take away a valuable tool that allowed the National Security Agency and other intelligence agencies to quickly and rapidly access phone records and match them up with other phone records to see who terrorists have been calling,” Rubio said.

Cruz denied Rubio’s claim that his support had made the US less safe.

“Marco knows what he is saying isn’t true,” Cruz said.

“What he knows is that the old program covered 20% to 30% of phone numbers to search for terrorists. The new program covers nearly 100%. That gives us greater ability to stop acts of terrorism and he knows that’s the case,” the Texan added.

Sen. Rand Paul (R-Kentucky), meanwhile, acted as a libertarian-minded agitator. He backed up Cruz and criticised Rubio for his opposition to the USA Freedom Act, as well as his support crafting a 2013 comprehensive immigration-reform bill along with Sen. Chuck Schumer (D-New York).

“Marco has more of an allegiance to Chuck Schumer and the liberals than he does to conservative policy,” Paul said.

Paul also went after New Jersey Gov. Chris Christie (R), who said that he’d be willing to institute a no-fly zone in Syria, and would shoot down Russian planes if they violated the zone.

“If you’re in favour of World War III, I think you’ve got your candidate,” Paul said referring to Christie, throwing in a jab over the governor’s so-called Bridgegate scandal.

Notably, however, two candidates that came into the debate with the most amount of tension — Cruz and Trump — managed to avoid criticising each other for another day. Last week, Cruz questioned Trump’s “judgment” at a closed-door event. Trump responded by unloading on Cruz.

When asked about his previous suggestion that Cruz may be “a little bit of a maniac” in the Senate, Trump brushed the comment off.

“He has a wonderful temperament. He’s just fine. Don’t worry about it,” Trump said, eliciting laughs from the crowd.

“You better not attack,” he told Cruz afterward, drawing another round of chuckles.

Cruz obliged.

NOW WATCH: Jeb Bush goes off on Trump after scrapping his trip to Israel

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.