By Jamie Coomarasamy
BBC News, Philadelphia
The posters on the walls of Philadelphia’s National Constitution Center, reading Clinton vs Obama, were designed to reinforce the impression of an impending prize fight - as was the opening salvo of the moderator, Charles Gibson.
Plenty of attention but no clear winner emerged from the verbal sparring
"We are in round 15 of a scheduled 10-rounder," he told the audience, using a boxing metaphor to describe the prolonged Democratic primary process.
That, at least, was the hype. Many of the previous presidential debates have failed to live up to their billing.
The bones of contention leading up to them have often been buried, once the candidates appeared on stage. The campaign rhetoric watered down, in the interests of party unity.
Here in Philadelphia, the gloves were off from the beginning, as the two ABC moderators, one of them a former press secretary to President Clinton, attempted to land as many blows as possible on the candidates.
The first 45 minutes saw both senators, especially Barack Obama, confronted with a list of character issues, raised in the run-up to next week's Pennsylvania primary.
The Illinois senator was immediately on the defensive, as he was pressed about his description of bitter, working class voters who "cling to guns and religion".
The two refused to be drawn on the issue of a running mate
He admitted that he had mangled his words, but said that he stood by the general thrust of his comments, arguing that the controversy they had engendered was an example of "old-style" Washington politics.
And he shot back with a reference to a verbal slip-up made by his opponent, not in this presidential campaign, but in the first one she fought, as a candidate's spouse, in 1992.
He said that her much-criticised remarks about women “staying home and baking cookies” had been taken out of context, just as his were being taken out of context now. By her.
It was one of the few times in the opening exchanges that the Illinois senator seemed comfortable.
He dealt far less deftly with the issue of his former pastor, Reverend Jeremiah Wright, giving what appeared to be evasive answers about the length of time he had taken to disown the controversial clergyman's more inflammatory remarks.
He had been far more confident when he appeared in the very same room, last month and responded to that controversy, with a generally well-regarded speech about race in America.
Hillary Clinton had to answer criticism, too. Most notably about her melodramatic and factually incorrect description of landing in Bosnia in 1996, under sniper fire, when she was first lady. She apologised again for her inaccuracy and said she was embarrassed by it.
But, in general, she had more opportunities than her opponent to join in with the moderators and pile criticism upon questioning, sometimes on issues, which have not figured prominently in the campaign.
This wasn't always to good effect.
When, for example, she questioned Barack Obama's association with a professor of education, who had once belonged to a far-left group that advocated planting bombs for political ends, her opponent shot back that President Clinton had actually pardoned two members of the same group.
When policy issues finally entered the debate, there were large areas of common ground.
Both candidates maintained that they would stick to their pledges to pull troops out of Iraq, whatever advice the generals gave them, and both advocated a diplomatic approach to Iran's nuclear programme.
On this, Hillary Clinton was rather more forceful, promising "massive retaliation" if Tehran were ever to launch an attack against Israel.
They also agreed that the person on the stage with them in Philadelphia would, if nominated, beat the Republican candidate, John McCain in November's general election. And they refused to make any commitment to have one another as a running mate.
This kind of negotiation may come at some point in the future. For the moment, though, the Democratic fight continues - an increasingly bitter war of attrition, which shows no immediate sign of ending.
This debate yielded plenty of punches, but no knock-out blows and, judging from the opinion polls, next week's vote in Pennsylvania may not be any more decisive.