The Republican presidential debate opened with a bang Wednesday night, with front-runners Rudy Giuliani and Mitt Romney immediately attacking each other on immigration. The CNN-YouTube debate in St. Petersburg, Fla., calmed down after the opening salvos, but still featured criticism and infighting among the eight candidates. The debate used video questions submitted by the public and included inquiries on immigration, conservative values, Iraq and economic issues. While previous debates’ competition appeared to be center around could attack Hillary Rodham Clinton the most, each candidate in this debate sought to come out ahead by contrasting himself with others on the crowded stage.

Most contentious issue: The subject of immigration dominated the first 20 minutes of the debate — the longest of any subject — and sparked some of the fiercest infighting among the candidates. In the very first question, New Yorker Ernie Nardi asked Giuliani whether as president he would continue to “aid and abet” illegal immigrants in the same manner he had as mayor of New York City.

Giuliani disagreed with the assertion that New York was a “sanctuary city” for illegal immigrants and said the city’s policies on the issue — which allowed the children of illegal immigrants to attend public schools, report crimes and receive emergency health care — filled a gap from the national level.

“The policies that we had were necessary because the federal policies weren’t working. The federal policies weren’t stopping people coming in to the United States. If I were president of the United States, I could do something about that,” he said.

After Romney got in on the attack — “This just happens to be a difference between Mayor Giuliani and myself and probably others on this stage,” — Romney said he felt illegal immigrants should have been reported for breaking the law rather than allowed to report other lawbreakers .

And then, Giuliani got personal.

“It’s unfortunate but Mitt generally criticizes people in situations in which he has had far the worse record,” Giuliani said, arguing that Romney had created a “sanctuary mansion” when he employed illegal immigrants to do work around his home .

“If you’re going to take this holier-than-thou attitude that you were perfect on immigration, it just so happens that you have a special immigration problem that nobody else up here has. You were employing illegal immigrants,” Giuliani said.

Most enthusiastic response: Illegal immigration opponent Rep. Tom Tancredo , on the immigration debate. “For a guy who usually stands on . . . the side and just listens all the time — that’s kind of frustrating in other debates — I have to tell you, so far it’s been wonderful because all I’ve heard is people trying to out-Tancredo Tancredo. It is great! I am so happy to hear it!”

The gun-loving-est candidate: With the Republican candidates stumbling over themselves to court the NRA vote, Duncan Hunter was quick to note he got his first hunting license at the age of 10 and mentioned his 20-gauge L.C. Smith shotgun. Fred Thompson appealed to gun owners’ love of discretion: “I own a couple of guns but I’m not going to tell you what they are or where they are,” he said, to some applause.

Best ducked answer: Mike Huckabee , a Baptist minister who also supports the death penalty. When asked, “What would Jesus do” about the death penalty, Huckabee responded: “Jesus was too smart to ever run for public office.”

Best table-turning response: Arizona Sen. John McCain , a prisoner of war during the Vietnam War, telling Romney he should oppose the practice of “waterboarding,” which he characterized as torture. Romney had said he did not endorse torture, but that he refused to outline which techniques he would or would not permit as president “so that the people that we capture will know what things we’re able to do and what things we’re not able to do.”

“Governor, let me tell you, if we’re going to get the high ground in this world and we’re going to be America that we have cherished and loved for more than 200 years, we’re not going to be torturing people,” McCain said.

He later added: “This is what America is all about. This is a defining issue, and clearly you should be able, if you want to be commander in chief of the U.S. armed forces, to take a definite and positive position on it. And that is, we would never allow torture to take place in the United States of America.”

Most creative question: From political cartoonist Nick Anderson of the Houston Chronicle, with an animation of Dick Cheney brandishing a shotgun, saying: “Will you grant your vice president as much power and influence as I’ve had? And remember, before you answer, I’m watching you.” Moderator Anderson Cooper directed the question to McCain and Thompson, neither said “yes.”

Best Yankees bashing: “Like all Americans, we love our sports teams and hate the Yankees” — former Massachusetts Gov. Mitt Romney , reacting to Giuliani’s love for the Bronx Bombers .