While they certainly spent time criticizing each other, the Republican presidential hopefuls devoted much time to criticize the Democratic frontrunner Senator Hillary Clinton. Former Massachusetts governor Mitt Romney said, "she hasn't run a corner store. She hasn't run a state. She hasn't run a city. She has never run anything. And the idea that she could learn to be President, you know, as an internship just doesn't make any sense." And Senator John McCain got a big round of applause for blasting Clinton and Senator Chuck Schumer's $1 million funding of a Woodstock memorial:

"Now, my friends, I wasn't there. I'm sure it was a cultural and pharmaceutical event. (LAUGHTER) I was tied up at the time."

McCain gave an ">extended version of that line to a crowd before the debate. and former NYC mayor Rudy Giuliani's Clinton attack? "We agree on two things. We're both Yankee fans. I'm a Yankee fan growing up in New York. She was a Yankee fan growing up in Chicago."

As for the barbs amongst each other, former senator Fred Thompson continued to poke holes in Giuliani's conservative stances, "Mayor Giuliani believes in federal funding for abortion. He believes in sanctuary cities. He’s for gun control. He supported Mario Cuomo, a liberal Democrat, against a Republican who was running for governor, then opposed the governor’s tax cuts when he was there.”

Giuliani came back and noted that Thompson "blocked tort reform over and over and over again. That is not a conservative position." Thompson later defended his record on tort reform and Giuliani zinged back at Thompson:

Oh, the simple fact is that New York City had a policy of allowing people who are illegal immigrants to report crime and to put their children in school. Otherwise, we reported every single illegal immigrant that committed a crime. The results had to be pretty darn good. I brought down crime by over 60 percent in New York City. I brought down homicide by 67 percent. I had the most legal city in the country. And I took the crime capital of America and I turned it into the safest large city in the country.

The senator has never had executive responsibility. He's never had the weight of people's safety and security on his shoulders.

I have. And I think I out-performed any expectations

You can read the transcript of the debate here.

Photographs of Republican candidates from left to right - Rep. Tom Tancredo, R-Colo., Rep. Ron Paul, R-Texas, former Arkansas Gov. Mike Huckabee, former New York City Mayor Rudy Giuliani, former Massachusetts Gov. Mitt Romney, former Sen. Fred Thompson, R-Tenn., Sen. John McCain, R-Ariz. and Rep. Duncan Hunter, R-Calif. - by John Raoux/AP