Obama wants to build on the current system, in which millions receive coverage through the workplace, with government funding to help uninsured families obtain coverage.

Obama also said that American International Group Inc., which was bailed out by the government, should give the Treasury $440,000 to cover the costs of a company retreat at a posh California resort less than a week after the federal intervention. "Those executives should be fired," he said, referring to the participants in the retreat.

The debate also veered into foreign policy, and the disputes were as intense as on the economy and domestic matters.

McCain said his rival "was wrong about Iraq and the surge. He was wrong about Russia when they committed aggression against Georgia. And in his short career he does not understand our national security challenges. We don't have time for on the job training."

Obama countered with a trace of sarcasm that he didn't understand some things — like how the United States could face the challenge in does in Afghanistan after spending years and hundreds of billions of dollars in Iraq.

The audience was selected by Gallup, the polling organization, and was split three ways among voters leaning toward McCain, those leaning toward Obama and those undecided.

Tom Brokaw of NBC, the moderator, screened their questions and also chose others that had been submitted online.