In contrast to their debate five days ago in Texas, Clinton and Obama butted heads from the opening moments, starting with a clash over whether the senator from Illinois had mischaracterized her plan for universal health care in his campaign mailings, and continuing throughout the 90-minute session.

"We should have a good debate that uses accurate information, not false, misleading and discredited information, especially on something as important as whether or not we will achieve quality, affordable health care for everyone," said Clinton (New York).

Obama pushed back with equal aggressiveness. "Senator Clinton has, in her campaign at least, has constantly sent out negative attacks on us, e-mail, robo-calls [prerecorded telephone messages], fliers, television ads, radio calls, and we haven't whined about it, because I understand that's the nature of this campaign," he said.