Rivals take aim at Clinton

Clinton took heat on the war in Iraq as well, even as she reiterated her measured plan to extricate the United States from that conflict. That plan has not satisfied some voters in the party's antiwar base.

"I will begin to bring our troops home as soon as I'm president," she said.

Obama, who described Clinton as having supported the war before she opposed it, said she was not the right person to undo the Bush policies. The key, he said, is having a president "who has not been one of the coauthors of this engagement in Iraq."

Edwards accused her of wanting to leave combat troops behind to wage combat missions and pointed to her unwillingness to set a timetable for complete withdrawal.

"You have choices, very clear choices," Edwards said. "I will get the troops out in my first year."

Other issues raised during the debate included education, energy policy, natural disasters, immigration, health care, tax policy and Social Security.

Despite the big-city setting, no special attention was given to urban issues by the questioners, Brian Williams and Tim Russert of NBC News.

Perhaps the best line of the night - in terms of the reception from the pro-Democratic crowd at Drexel's Main Building Auditorium - came from Biden, who has made no secret of his contempt for the idea that Republican Rudy Giuliani might get elected president.

"All he says is a noun and a verb and 9/11; there's nothing else," Biden said. "He is genuinely not qualified to be president."