The Texas congressman launched ferocious attacks against Rick Santorum, who has surged in the polls recently, and Newt Gingrich.
Those two snapped back, leading to one of the most testy exchanges in the debate, and all frontrunner Mitt Romney had to do was sit back and watch his rivals tear each other down.
Paul, who is second in New Hampshire polls, got plenty of air time to make his attacks and all of the candidates involved in the exchanges found themselves playing defense against each other.
Paul has pounded Santorum since the former senator has surged in the polls, and he kept it up during Saturday night's debate.
Paul, who has called Santorum a "liberal" because of his record on voting for government spending, was asked if he stood by an ad from his campaign calling Santorum "corrupt."
He responded by calling Santorum one of the "top corrupt individuals because he took so much money from the lobbyists."
But his argument was interrupted by feedback from his microphone, causing Santorum to quip: "They caught you not telling the truth, Ron."
While that remark was funny, the former senator also gave a former response, attacking Paul's record for supporting earmarks.
"As a senator from Pennsylvania that I had a responsibility to go out there and represent the interests of my state. And that's what I did to make sure that Pennsylvania was able, in formulas and other things, to get its fair share of money back. I don't apologize for that any more than you did when you earmarked things and did things when you were a congressman in Texas," he said.
Paul wouldn't back down: "You're a big-government conservative. And you don't vote for, you know, right to work and these very important things. And that's what weakens the economy. So to say you're a conservative, I think, is a stretch. But you've convinced a lot of people of it, so somebody has to point out your record."
Santorum snapped back: "I think I have an opportunity to respond here. I've convinced a lot of people of it because my record is actually pretty darn good. … You vote against everything. I don't vote against everything. I do vote for some spending. I do think government has a role to play."
Texas Gov. Rick Perry used that exchange to note: "You've just seen a great example of why I got in this race, because I happen to think that I'm the only outsider, with the possible exception of Jon Huntsman, who has not been part of the problem in Washington, D.C., the insiders in Washington, D.C."
He also accused Paul of being a hypocrite: "Here's what frustrates me, is that you go get the earmarks and then you vote against the bill? Now, I don't know what they call that in other places, but, Congressman Paul, in Texas, we call that hypocrisy."
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Paul was quick to answer: "Well, I call it being a constitutionalist, because I believe we should earmark, or designate, every penny."
Gingrich was also critical of Paul. When asked about Paul calling him a "chickenhawk" because he didn't serve in the military, the former speaker said: "Dr. Paul makes a lot of comments. It's part of his style."
Paul wouldn't back down. "I think people who don't serve when they could and they get three or four or even five deferments, they have no right to send our kids off to war," he said. "I'm trying to stop the wars, but
at least, you know, I went when they called me up."
Gingrich looked angry and said he resented Paul's remarks.
"Dr. Paul has a long history of saying things that are inaccurate and false. The fact is, I never asked for deferment. I was married with a child. It was never a question. My father was, in fact, serving in Vietnam in the Mekong Delta at the time he's referring to. I think I have a pretty good idea of what it's like as a family to worry about your father getting killed. And I personally resent the kind of comments and aspersions he routinely makes without accurate information and then just slurs people with," he said.
Paul injected: "When I was drafted, I was married and had two kids, and I went."
The audience strongly applauded that statement and over the noise Gingrich said, "I wasn't eligible for the draft. I wasn't eligible for the draft."