While the GOP debate dissolved into shouting matches on multiple occasions Tuesday night, some of the most visceral bickering erupted on the topics of illegal immigration and the border fence.

Texas Gov. Rick Perry  came out swinging  against former Massachusetts Gov. Mitt Romney, attacking him for being “one of the problems” when it comes to illegal immigration.

“Mitt, you lose all of your standing, from my perspective, because you hired illegals in your home and you knew about it for a year,” Perry said.” And the idea that you stand here before us and talk about that you’re strong on immigration is on its face the height of hypocrisy.”

To which Romney responded,  ”I don’t think I’ve ever hired an illegal in my life.”

The two candidates then shouted over one another, with Romney chastising Perry for having “a problem with allowing someone to finish speaking” and Perry cutting Romney off, saying “I’ll tell you what the facts are.”

Eventually,  Romney explained  that “we went to the company and we said, ‘Look, you can’t have any illegals working on our property.’”

“I’m running for office, for Pete’s sake, I can’t have illegals,” Romney added.

The former Massachusetts governor later turned the attack back on Perry, saying his record on immigration “doesn’t stand up to muster” because “Texas has had 60 percent increase in illegal immigrants” in the past 10 years.

“Gov. Perry, you say you have got the experience,” Romney said. “It’s a bit like saying that, you know, the college coach that has lost 40 games in a row has the experience to go to the NFL.”

Rep. Michele Bachmann of  Minnesota also joined in the attacks on Perry, emphasizing that unlike the Texas governor, she “will build a double-walled fence” that stretches along ”the entire border.”

Besides Rep. Ron Paul of Texas, Perry was the only GOP candidate on stage who opposes a fence along the entire 2,000-mile U.S.-Mexico border.

“You know, for someone that’s been in the United States Congress, to lecture me on the issues that are going on, on that border is not right,” Perry shot back. “Let me tell you, we’ve had to deal with that issue in the state of Texas. We’ve had to deal with the impact on our state. We know how to secure the border.”

Herman Cain was also quick to point out his support of a full-border fence, but backed away from comments he made this weekend that the fence should be ”20 feet high, with barbed wire, electrified. With a sign on the other side that says it can kill you.”

“Yes, I believe we should secure the border for real, and it would be a combination of a fence, technology, as well as possibly boots on the ground for some of the more dangerous areas,” Cain said at Tuesday’s Las Vegas debate, adding that he does not “apologize at all for wanting to protect the American citizens.”

The former Godfather’s Pizza CEO had said two days before that his electric fence comments were only a “joke” but, by Monday, Cain again reiterated that he supported a fence that “might be electrified.”

In a Tuesday speech at the libertarian Cato Institute, former Mexican President Vicente Fox  slammed Cain’s electric fence idea, saying it was “incredible,” “stupid” and “nonsense.” Fox said he might as well put “water with crocodiles” along the border.

Perry also pushed back against Cain’s plan, saying at the debate that “there’s a better way.”

“I will tell you, Herman, you put a lot of boots on the ground,” Perry said. “You use Predator drones that are being trained right up here at Creech Air Force Base in Nevada to use that real-time information to give those boots on the ground that information, and they can instantly move to those areas. And that is the way to shut that border down, to secure that border.”