"I think some of this stuff gets overhyped," Obama said. In a Philadelphia movie reference, he added, "In fact, I think this has been the most hyped fight since Rocky fought Apollo Creed, although the amazing thing is I'm Rocky in this situation."
The sharp exchanges mark a more intense phase of the battle for the Democratic nomination, with barely two months left before Iowans cast the first votes for president.
Gov. Bill Richardson, D-N.M., was one of the few candidates to come to Clinton's defense.
"I'm hearing this holier-than-thou attitude toward Senator Clinton," Richardson said. "That is bothering me because it's pretty close to personal attacks that we don't need. Do we trust her? Do we -- she takes money from special interests. We need to be positive in this campaign. Yes, we need to point out our differences, and I have big differences with her."
While most of those on stage focused on Clinton, Sen. Joe Biden, D-Del., took aim at the Republican frontrunner, former mayor Rudolph Giuliani, R-N.Y.
"Rudy Giuliani -- there's, there's only three things he mentions in a sentence: a noun and a verb and 9/11. I mean, there's nothing else," Biden said. "Rudy Giuliani -- probably the most underqualified man since George Bush to seek the presidency."
Though Clinton said the attacks she's getting from Republicans speak to her history fighting for Democratic causes, her rivals had their own opinions about why they keep bringing up her name.
"They may actually want to run against you, and that's the reason they keep bringing you up," Edwards said. "Will she be the person who brings about the change in this country? You know, I -- I believe in Santa Claus, I believe in the Tooth Fairy, but I don't think that's going to happen. I really don't. And I -- I think that if people want the status quo, Senator Clinton's your candidate."
Obama's theory: "Part of the reason that Republicans, I think, are obsessed with you, Hillary, is because that's a fight they're very comfortable having. It is the fight that we've been through since the '90s."
Sen. Chris Dodd, D-Conn., argued that Clinton may not be electable. "Whether it's fair or not fair, the fact of the matter is that my colleague from -- from New York, Senator Clinton, there are 50 percent of the American public that say they're not going to vote for her."
Rep. Dennis Kucinich, D-Ohio, made perhaps the most startling admission of the night, when asked by moderator Tim Russert whether he in fact saw a UFO.
"I did," he said. "It was unidentified flying object, OK. It's like -- it's unidentified. I saw something."