From Sunny looking over comments on Debate last night:

It was the seventh time the candidates had met and it was strikingly different in tone from any of the prior debates. At times, it seemed that Mrs. Clinton was parrying criticism from every corner of the stage, reflecting the vulnerabilities that come from being a high-visibility candidate who has built large leads in national polls with just two months to go until the first vote.

Mrs. Clinton was attacked for not offering specific plans on what she might do with Social Security. She was challenged for voting to designate the Iranian Revolutionary Guard as a foreign terrorist organization. She was assailed at one moment as being disingenuous, the next as a symbol of tired Washington establishment and the next for being unelectable.

At one point, she appeared to say she supported an attempt by Gov. Eliot Spitzer of New York to give driver’s licenses to illegal immigrants, a plan he abandoned in the face of fierce opposition. A moment later she backed off, leading her opponents to denounce her again for obfuscating.

The tone of the debate, which was sponsored by NBC News, had been established before the candidates walked onto the stage at Drexel University in Philadelphia, when Senator Barack Obama of Illinois proclaimed in an interview over the weekend that “now is the time” to begin drawing tough distinctions with Mrs. Clinton.

He did so almost immediately, accusing Mrs. Clinton of “changing positions whenever it’s politically convenient,” pointing to the North American Free Trade Agreement, torture and the war on Iraq. “Now, that may be politically savvy, but I don’t think that it offers the clear contrast that we need,” Mr. Obama said. “I think what we need right now is honestly with the American people about where we would take the country.”

But for all the attention Mr. Obama drew to himself coming into the debate, he was frequently overshadowed by former Senator John Edwards of North Carolina, who — speaking more intensely — repeatedly challenged Mrs. Clinton’s credentials and credibility, and frequently seemed to make the case against Mrs. Clinton that Mr. Obama had promised to make.

“Senator Clinton says that she believes she can be the candidate for change, but she defends a broken system that’s corrupt in Washington, D.C.,” Mr. Edwards said.

He added, “I think the American people, given this historic moment in our country’s history, 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.”

The debate appeared to mark a turning point in the Democratic contest, as Mrs. Clinton’s rivals feel increasing pressure to begin trying to weaken her as the first voting approaches.

Though there were a few light moments — Representative Dennis C. Kucinich of Ohio said he had once seen a U.F.O. — the tone of the night was tense and combative.

Mrs. Clinton walked into the debate expecting to be the target of attacks but as the night went on, she appeared surprised by the intensity as she was challenged not only by her opponents but by the moderators, Brian Williams and Tim Russert of NBC.

Mrs. Clinton smiled far less frequently than she had in earlier debates, often looking grim as she turned her head from Mr. Edwards to her right to Mr. Obama on her left. “I need to rebut that,” she said at one point. “I don’t know where to start.”

Mrs. Clinton pointed to the fact that Republicans have been assailing her constantly as evidence that she was delivering a clear message.

“The Republicans and their constant obsession with me demonstrates clearly that they obviously think that I am communicating effectively about what I will do as president,” she said. “And I am trying to do that because it matters greatly. We’ve got to turn the page on George Bush and Dick Cheney. In fact, we have to throw the whole book away. This has been a disastrous period in American history, and we hope it will be aberration.”

The attacks on Mrs. Clinton grew so intense that one opponent, Gov. Bill Richardson of New Mexico, who served in President Bill Clinton’s administration, scolded the others. “You know what I’m hearing here, I’m hearing this holier-than-thou attitude toward Senator Clinton,” he said. “It’s bothering me because it’s pretty close to personal attacks that we don’t need.”

“But the important thing is that we need to stay positive,” Mr. Richardson said. “We need to have disagreements on the issues, not on whether you can trust. I trust Senator Clinton but I don’t agree with her on a majority of issues.”

Mr. Edwards and Mr. Obama almost stumbled over each other in offering a different interpretation of the Republican attacks on Mrs. Clinton than the one she offered.

“Part of the reason that Republicans, I think, are obsessed with you, Hillary, is because that’s a fight they’re very comfortable having,” Mr. 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.”