Edwards accused Clinton and Obama of timidity during the recent debate over the war funding bill in Congress. The two senators voted against the bill, but waited until the last moment to declare their intentions.

"Others on this stage — Chris Dodd spoke out very loudly and clearly," Edwards said of the senator from Connecticut. Then, making clear he was talking about Obama and Clinton, he added: "Others did not. Others were quiet. They went quietly to the floor of the Senate, cast the right vote. But there is a difference between leadership and legislating."

Obama shot back that Edwards, as a senator, had supported the 2002 resolution authorizing the war. "The fact is, is that I opposed this war from the start," Obama said. "So you're about 4 1/2 years late on leadership on this issue."

Clinton deflected the question, saying the real division over Iraq is between the two parties. "The differences among us are minor," she said. "The differences between us and the Republicans are major. And I don't want anybody in America to be confused."

The brisk exchange over Iraq highlighted a defining feature of the two-hour debate: It brought the top three Democratic contenders into close proximity and gave them their first real chance to joust in public. Although all eight Democratic candidates participated, debate sponsors deliberately put Clinton, Obama and Edwards next to each other, and they took much of the limelight.

Obama gave a more commanding performance Sunday night than he did during the first Democratic debate, in South Carolina in April. He stepped in to respond confidently to his colleagues, challenging their answers on Iraq and health care, the two central issues of the debate.

Clinton seemed as forceful as she was in the first debate, while Edwards played the role of the aggressor in drawing distinctions with the others. He has been doing so from a distance throughout the campaign, but on Sunday night he did not shy from calling out his rivals directly.

Gov. Bill Richardson of New Mexico emphasized his experience at the state level, saying that as chief executive he had achieved results on health care and learned firsthand about the issues involved in immigration. Dodd, by contrast, emphasized his more than two decades in the Senate.

Sen. Joseph R. Biden Jr. (Del.) showed off his expertise as chairman of the Foreign Relations Committee, demanding clear action on the humanitarian crisis in the Darfur region of Sudan and cautioning that Democrats do not now have the votes in Congress to end the war. "Ladies and gentlemen, you're going to end this war when you elect a Democratic president," he said.

But Biden defended his decision to vote for continued funding for the military in Iraq; he was the only Democrat on stage to have done so. Although he declined to criticize his colleagues, Biden said: "Look, I cannot — as long as there is a single troop in Iraq that I know if I take action by funding them, I increase the prospect they will live or not be injured — I cannot and will not vote no to fund them."

Rep. Dennis J. Kucinich (Ohio), an antiwar protest candidate, said Congress has the power to end the war. "Just say, 'No money, the war is over,' " he said.

Former senator Mike Gravel (Alaska) accused Democrats of complicity in Iraq. "Sure, it's George Bush's war. But it's the Democrats' war also," he said.

Both Clinton and Edwards faced questions about the fact that they did not read the National Intelligence Estimate preceding the 2002 vote authorizing the invasion. Clinton said she had been "thoroughly briefed" at the time and "sought dissenting opinions" on her own.

Edwards, likewise, said he had all "the information I needed" to make a decision. But then he again pressed Clinton for refusing to call her vote a mistake. "I think it is important for anybody who seeks to be the next president of the United States, given the dishonesty that we've been faced with over the last several years, to be honest to the country," he said.

Clinton — who according to a new Washington Post-ABC News poll holds a solid lead over her Democratic rivals nationally but trails in some statewide surveys in early primary states — referred to her husband's administration several times during her answers and fielded questions about him as well.

Asked whether his administration's "don't ask, don't tell" policy for gays in the military was a mistake, Clinton described it as a necessary political compromise at the time but an inadequate policy today. "It was a transition policy," Clinton said, adding she believes that the policy could be changed to allow gays to serve openly in the military.

In another exchange over military policy, Clinton differed with Edwards over the term "global war on terror," which Edwards has dismissed as a politically charged bumper-sticker slogan. "That's all it is, all it's ever been — was intended to do was for George Bush to use it to justify everything he does: the ongoing war in Iraq, Guantanamo, Abu Ghraib, spying on Americans, torture," Edwards said. "None of those things are okay. They are not the United States of America."

Asked if she agreed with Edwards, Clinton responded, "No, I do not."

"I am a senator from New York," she said. "I have lived with the aftermath of 9/11, and I have seen first hand the terrible damage that can be inflicted on our country by a small band of terrorists who are intent upon foisting their way of life and using suicide bombers and suicidal people to carry out their agenda."

On health care, the discussion opened with a question about the cost of providing universal coverage. It quickly expanded to a debate about how to achieve that goal.

Edwards said his plan would cost $90 billion to $120 billion a year, and he pledged to roll back Bush's tax cuts for Americans earning more than $200,000 a year. "I believe you cannot cover everybody in America, create a more efficient health care system, cover the cracks, you know, getting rid of things like pre-existing conditions and making sure that mental health is treated the same as physical health; I don't think you can do all those things for nothing."

Obama, responding to criticism from Edwards that his plan would not provide universal coverage, said he prefers to make insurance more affordable to average Americans rather than make it mandatory. "My belief is that most families want health care but they can't afford it," he said.

Clinton said she is "thrilled" Democrats have again embraced the goal of universal coverage, after she and her husband could not get their health-care bill through Congress in 1994. She said what is most needed is political support to weather attacks of the kind that killed their plan.

"You've got to have the political will — a broad coalition of business and labor, doctors, nurses, hospitals — everybody standing firm when the inevitable attacks come from the insurance companies and the pharmaceutical companies that don't want to change the system because they make so much money out of it," she said.

At one point, the candidates were asked whether they favor making English the official language of the country. All but Gravel opposed the idea, but Obama used the query to make a broader point, saying such questions are designed to divide the country. "When we get distracted by those kinds of questions," he said, "I think we do a disservice to the American people."