In their most contentious debate yet, the eight Republican contenders for the White House were forced to tackle tough questions on Iraq, torture and illegal immigration.
And in another indication the Republican nomination is truly up for grabs, their toughest interrogators were each other.
'Sanctuary City' vs. 'Sanctuary Mansion'
The CNN/YouTube sponsored debate in St. Petersburg, Fla., kicked off with a contentious and angry exchange between front-runners Rudy Giuliani and Mitt Romney on immigration.
"The reality is that New York City was not a sanctuary city," former New York Mayor Rudy Giuliani said in response to a question posed by Ernie Nardi of Dyker Heights in Brooklyn, New York.
Romney, the former governor of Massachusetts, quickly took issue with Giuliani's contention.
"[New York] called itself a sanctuary city. And as a matter of fact, when the welfare reform act that President Clinton brought forward said that they were going to end the sanctuary policy of New York City, the mayor actually brought a suit to maintain its sanctuary city status," Romney contended.
"It's unfortunate, but Mitt generally criticizes people in a situation in which he's had [by] far the worst record. … There was even a sanctuary mansion. At his own home, illegal immigrants were being employed, not being turned into anybody or by anyone."
That was a reference to Romney employing a landscaping company that employed illegal Guatemalan immigrants at his pink colonial mansion in Belmont, Mass.
Romney shot back, "I think it is really kind of offensive actually to suggest, to say look, you know what, if you are a homeowner and you hire a company to come provide a service at your home — paint the home, put on the roof. If you hear someone that is working out there, not that you have employed, but that the company has."
Moments later, Romney said, "Mayor, you know better than that," before adding this to the Brooklyn-born Giuliani, "If you hear someone with a funny accent, you, as a homeowner, are supposed to go out there and say, 'I want to see your papers?'"
Thompson Attacks, Huckabee Smiles
Former Tennessee Sen. Fred Thompson also got into the act, going after Giuliani and targeting Romney as a flip-flopper.
"Gov. Romney supported the Bush immigration plan until a short time ago. Now he's taken another position, surprisingly," the actor-turned-politician declared.
Even more intriguing, Thompson took his free 30 seconds for his YouTube video to run an attack ad — the first one of the season — against Romney for once supporting abortion rights and former Arkansas Gov. Mike Huckabee, surging in Iowa, for having raised taxes.
"What's up with that?" asked debate moderator Anderson Cooper.
"I just wanted to give my buddies here a little extra airtime," Thompson dryly replied. "Listen, I mean, what do you mean what's up with it? These are their words."
Huckabee's rising star brought several incoming shots. He was asked about scholarships he supported for the children of illegal immigrants.
"This bill would've said that if you came here, not because you made the choice but because your parents did, that we're not going to punish a child because the parent committed a crime," Huckabee explained.
Romney, fighting with Huckabee for the lead in the first caucus state of Iowa, replied, "Mike, that's not your money. That's the taxpayers' money."
McCain Engages Ron Paul
Arizona Sen. John McCain played with populist fire, engaging Texas Rep. Ron Paul on his opposition to the Iraq War and plan to withdraw troops.
McCain, who has staked his political career on his support for the surge in Iraq and fight against global Islamic terrorism, said directly, "Congressman Paul, I've heard him now in many debates talk about bringing our troops home and about the war in Iraq and how it's failed and I want to tell you that that kind of isolationism, sir, is what caused World War II."
McCain continued after a mixed round of applause and jeers from the debate crowd, "We allowed Hitler to come to power with that kind of attitude of isolationism."
Paul, who recently raised $4 million exclusively from online contributors, calmly asked McCain, "The real question you have to ask is why do I get the most money from active duty officers, military personnel?"
"So what John is saying is just totally distorted. He doesn't understand the difference between nonintervention and isolationism. I'm not an isolationist. I want to trade with people, talk with people, travel. But I don't want to send our troops overseas using force telling them how to live. We would object to it here and they're going to object to us over there."
It was not the first time the two men tangled.
Recalling Iraq again at a later point in the debate, McCain asserted, "We never lost a battle in Vietnam. It was American public opinion that caused us to lose that conflict."
McCain then said that the difference between Iraq and Vietnam is al Qaeda's determination to attack the United States.
"They want to follow us home, they want Iraq to be a base for al Qaeda," McCain insisted.
Paul engaged McCain once again, saying that whether or not the United States "never lost a battle" in Vietnam is "irrelevant."
"[Al Qaeda] want to come here … because of our military base in Saudi Arabia," Paul retorted.
"They come here because we're occupying their country just as we would object if they occupied our country," he added.
In many instances the disagreement among the eight Republican contenders were not just political arguments, but tangible disdain.
McCain, a Vietnam veteran who spent nearly five years in a POW prison camp, also had sharp differences with Romney on whether waterboarding should be declared illegal.
"I am astonished that you would think such a, such a torture would be inflicted on anyone in our — who we are held captive (sic) and anyone could believe that that's not torture," McCain said.
Giuliani Defends Money Mess
Before the debate, Republicans were buzzing about a story that broke Wednesday afternoon claiming that Rudy Giuliani had misused public funds when he was mayor of New York to pay for secret trips to the Hamptons with his then-mistress and future wife Judith Nathan.
The story, first published by the political newspaper Politico, included a claim by New York City Comptroller William Thompson that his auditors "were unable to verify that these expenses were for legitimate or necessary purposes."
Giuliani vigorously denied the accusation.
"First of all, it's not true. I had 24-hour security for the eight years I was mayor," he said. "I had nothing to do with the handling of their records, and they were handled, as far as I know, perfectly appropriately."
There were several fun YouTube moments.
One questioner asked, "For those of you who would call yourselves Christian conservatives, the death penalty, what would Jesus do?"
Huckabee, a Baptist minister before he entered political life, responded with characteristic wit and deft political awareness, "Jesus was too smart to ever run for public office. … That's what Jesus would do."
ABC News' Ed O'Keefe, Jan Simmonds and Z. Byron Wolf contributed to this report.