She appeared to be the most comfortable of the eight runners in the 90-minute televised debate from the South Carolina university campus as she dealt with a series of questions ranging from how she would handle another terrorist attack on the US to her vote in 2002 backing the invasion of Iraq.

"If we are attacked, and we can determine who is behind that attack, and if there are nations that supported or gave material aid to those who attacked us, I believe we should quickly respond," she said.

But she added she would not go looking for other fights as George Bush had done in Iraq. "It is not a decision that I would have made, had I been president, because we still haven't found Bin Laden."

The dominant themes for all the candidates - and the ones that resonated most with the audience - were opposition to the Iraq war, promises to introduce universal health care and better checks on the background of those buying guns in the wake of the Virginia Tech killings. Abortion, tax and immigration were also discussed.

None of the candidates made any serious gaffes or gave the kind of distrastrous performance that can alter the course of a campaign.

Mr Obama and the third of the frontrunners, John Edwards, started slowly and stumbled on a few occasions, particularly on how to respond to any new terrorist attacks. Mr Obama, who has been gaining in most of the polls and has matched Mrs Clinton in fundraising, showed little of the dynamic rhetoric on which he has built his reputation.

He regained a little ground towards the end in a series of spirited exchanges with Denis Kucinich, who is fervently anti-war, over Mr Obama's refusal to rule out military action against Iran.

"You're setting the stage for another war," Mr Kucinich said.

Mr Obama responded: "I think it would be a profound mistake for us to initiate a war with Iran. But have no doubt, Iran possessing nuclear weapons will be a major threat to us and to the region."

That was one of the genuine exchanges. Although billed as a debate, the event turned out to be more a series of quick-fire audience questions to the candidates restricted to one-minute and even single sentence answers.

There were also gimmicks, with the candidates asked for a show of hands on questions such as whether they have ever had a gun in their homes. Mrs Clinton, Mr Obama and Mr Edwards had not. In the crowded "spinroom", the traditional venue for exchanges between journalists and campaign advisers afterwards, Mrs Clinton's team left an impression of being the most satisfied with the outcome.

Mandy Grunwald, one of Mrs Clinton's advisers, said: "She was the most presidential. I would not say there were losers, she was the strongest candidate."

Robert Gibbs, Mr Obama's communications chief, said: "I was surprised there was not a little more mixing it up." He described the show of hands as "awkward".

The main aim at this stage, with the election of the Democrat candidate 263 days away, was for the frontrunners to avoid making mistakes - which they did - and for the second and third tier candidates Mr Kuchinich, Joe Biden, Bill Richardson, Chris Dodd and Mike Gravel to make an impression - which they failed to do.

The consensus among students watching the debate was summed up by 18-year-old Sharonda Richards. "Overall, Hillary did best. I was disappointed in Obama. Before I was torn betweeen Hillary and Obama," she said.

The debate was free of personal abuse and Mr Biden got the laugh of the night. He was called on to respond to an accusation that he was too verbose and asked whether he could provide an assurance to voters he "would have the discipline you would need on the world stage".

"Yes," Mr Biden said, refusing to utter another word.