PHILADELPHIA, Pennsylvania (CNN) -- The night fittingly began with a reference to "Rocky" in the fictional boxer's hometown, as the Democratic presidential debate Tuesday at times took on the feel of a heavyweight fight.
Former Sen. John Edwards, left, and Sen. Barack Obama criticized Sen. Hillary Clinton in the debate.
Illinois Sen. Barack Obama, who this week said he would sharpen attacks on front-runner and New York Sen. Hillary Clinton, first called their differences "overhyped."
He joked, "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."
Moments later, the tone changed as he launched the first of a series of attacks on Clinton, claiming the 2008 presidential race "requires us to be honest about the challenges that we face. It does not mean, I think, changing positions whenever it's politically convenient." Watch the candidates exchange sharp words »
Former North Carolina Sen. John Edwards criticized Clinton for her stance on Iraq, Iran and Social Security.
"The American people ... deserve a president of the United States that they know will tell them the truth and won't say one thing one time and something different at a different time," Edwards said.
Held just over two months before the first primaries, the debate at Drexel University was the Democrats' first face-off since tangling at Dartmouth College in New Hampshire a month ago. Since then, Clinton has solidified her status as front-runner -- and primary debate target.
Edwards said Clinton's support for a resolution labeling the Iranian Revolutionary Council a terrorist organization was calculated, as she was "moving from primary mode to general election mode."
"I think that our responsibility as presidential candidates is to be in 'tell the truth' mode all the time," Edwards said.
Clinton defended her "record of 35 years fighting for women and children and people who feel invisible and left out in this country."
"I don't think the Republicans got the message that I'm voting and sounding like them," Clinton said.
"If you watched their debate last week, I seemed to be the topic of great conversation and consternation. And that's for a reason, because I have stood against George Bush and his failed policies."
Obama offered a different explanation. "Part of the reason that Republicans, I think, are obsessed with you, Hillary, is because that's a fight they're very comfortable having," Obama said.
'"It is the fight that we've been through since the '90s. And part of the job of the next president is to break the gridlock and to get Democrats and independents and Republicans to start working together to solve these big problems like health care or climate change or energy."
But, said Edwards, "another perspective on why the Republicans keep talking about Sen. Clinton is, Senator, they may actually want to run against you."
Edwards blasted Clinton for being the candidate who has raised the most money from special interests and lobbyists.
"Will she be the person who brings about the change in this country? You know, I believe in Santa Claus. I believe in the tooth fairy," Edwards said. "But I don't think that's going to happen."
Clinton, however, said she is the candidate who has laid out specific plans, with the qualifications to deliver.
"Change is just a word if you don't have the strength and experience to actually make it happen," she said.
Asked about New York Gov. Eliot Spitzer's controversial plan to give driver's licenses to illegal immigrants, Clinton said it "makes a lot of sense" but stopped short of endorsing the plan.
"We want to know who's in New York," she said. "We want people to come out of the shadows."
Edwards claimed Clinton's answer was inconsistent. And Sen. Chris Dodd called the plan "troublesome," adding that "a license is a privilege, and that ought not to be extended, in my view."
New Mexico Gov. Bill Richardson came to Clinton's defense at one point, saying he was bothered by other candidates' "holier than thou" attitude toward her.
"It's pretty close to personal attacks that we don't need," said Richardson, who served as energy secretary in the Clinton administration.
Iraq, Iran dominate foreign policy discussion
Clinton and Edwards clashed over the next step for U.S. troops and their role in Iraq.
"If you believe there should be no actual timetable for withdrawal, then Sen. Clinton is your candidate," Edwards said, adding "we need to get combat troops out of Iraq."
Clinton claimed Edwards misstated her position.
"My understanding is that we had the same agreement -- most of us on this stage -- that we would bring out combat troops, but we would pursue a mission against al Qaeda in Iraq, if they remained a threat."
Clinton defended her support of the resolution declaring the Iranian Revolutionary Council a terrorist organization.
"I am not in favor of this rush for war, but I'm also not in favor of doing nothing. Iran is seeking nuclear weapons," Clinton said.
Obama, who did not vote on the resolution, criticized it as premature.
"This kind of resolution does not send the right signal to the region," he said.
Edwards ridiculed Clinton for saying she wanted to "maximize pressure on the Bush administration."
"So the way to do that is to vote yes on a resolution that looks like it was written, literally, by the neocons," the former North Carolina senator asked.
The candidates outlined their approaches on Iran, with Richardson advocating negotiations with Tehran without conditions and saying the world "cannot permit Iran to use nuclear weapons."
Dodd said the situations amplify the need for foreign policy experience and suggested he was the candidate who could deliver that experience.
In a lighter moment, Ohio Rep. Dennis Kucinich confirmed an account in actress Shirley MacLaine's book that he saw a UFO while at her home in Washington state. Watch Kucinich describe his close encounter »
"More people in this country have seen UFOs than I think approve of George Bush's presidency," he said. E-mail to a friend
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