US:An aid worker in Darfur, a lesbian couple in Brooklyn, a woman with breast cancer and a talking snowman worried about climate change were among the questioners when YouTube users quizzed Democratic candidates for two hours in the most innovative debate since the 2008 presidential campaign began.
The CNN/YouTube debate at The Citadel, an elite military college in Charleston, South Carolina, provoked sharp exchanges among the candidates as they were pressed for frank answers on everything from sex education in schools to healthcare and the war in Iraq.
Although Barack Obama gave his strongest performance in a debate so far, and John Edwards showed populist passion, the debate did little to dislodge Hillary Clinton from her position as the frontrunner for the Democratic nomination.
Mr Obama used a question about the difficulties of withdrawing from Iraq to make a sharp jab at Mrs Clinton, who has never disowned her 2002 vote to authorise the war. "The time for us to ask how we were going to get out of Iraq was before we went in," he said to applause.
"And that is something that too many of us failed to do. We failed to do it. And I do think that that is something that both Republicans and Democrats have to take responsibility for."
Mr Obama lost his advantage later, however, when he was asked if he would agree to meet the leaders of Iran, Syria, North Korea, Cuba and Venezuela within a year of becoming president. Mr Obama said he would and Mrs Clinton pounced, declaring that she would not promise such a high-level meeting until she knew what the other side's intentions are.
"I don't want to be used for propaganda purposes," she said.
"I will purse very vigorous diplomacy. And I will use a lot of high-level presidential envoys to test the waters, to feel the way.
"But certainly, we're not going to just have our president meet with Fidel Castro and Hugo Chavez and, you know, the president of North Korea, Iran and Syria until we know better what the way forward would be."
In the spin room after the debate, Clinton campaign staff seized on the exchange as evidence that their candidate had the strength and experience needed for the presidency, implying that Mr Obama lacked it. "She showed that she's ready to be president," said Clinton pollster Mark Penn.
Dismissing the dispute as "a distinction without a difference", Obama strategist David Axelrod insisted that Mr Obama and Mrs Clinton were essentially saying the same thing, although the transcript does not support that interpretation.
The questions, posed in 30-second home-made videos, included a plea for an end to the war from a father who had lost a son in Iraq, and a demand for reparations for slavery (which only left-wing congressman Dennis Kucinich supported).
When Mr Obama was asked about suggestions that he was not quite "black enough", he replied to laughter that, "when I'm catching a cab in Manhattan - in the past, I think I've given my credentials."
Mrs Clinton dismissed fears that she would not be acceptable as president in Muslim countries by detailing her record of high-level meetings as first lady and later as a senator.
"I have met with many officials in Arabic and Muslim countries. I have met with kings and presidents and prime ministers and sheikhs and tribal leaders," she said. "I believe that there isn't much doubt in anyone's mind that I can be taken seriously."
Mrs Clinton's clear lead in the polls ensured that her rivals took her seriously enough to attack her for compromising with special interests and Mr Edwards said that the US needed a more radical departure than she is promising.
"Do you believe that compromise, triangulation will bring about big change? I don't," he said. "I think the people who are powerful in Washington - big insurance companies, big drug companies, big oil companies - they are not going to negotiate. They are not going to give away their power. The only way that they are going to give away their power is if we take it away from them."
Joe Trippi, who managed Howard Dean's campaign in 2004 and now advises Mr Edwards, said later that he was relaxed about his candidate's third-place status, which he predicted would not change until after the Iowa caucuses next January.
"I'm living proof that none of these polls matter. Four years ago, Howard Dean was going to win the nomination," he said. "People really want to change the place. They don't just want to change one party's establishment with another."
After the debates, Google, which owns YouTube, transformed a bus terminal into a vast, dimly-lit lounge with deep-pile carpets for a late-night party with loud music and free cocktails.
None of the leading candidates were there - they were at smaller gatherings around the city, hosted by other corporate sponsors.