So whom is an uninsured voter to believe?

In one of the liveliest exchanges of the Democratic debate last night, Senator Hillary Rodham Clinton said that Senator Barack Obama’s health care plan “would leave 15 million Americans out.” That, Mrs. Clinton added in an ominous nod to the early nominating states, is “about the population of Nevada, Iowa, South Carolina and New Hampshire.” Mr. Obama countered that “the fact of the matter is that I do provide universal health care.”

The crux of their dispute centers on their overall approaches to health care.

Mrs. Clinton’s plan would require all Americans to get coverage and would provide subsidies to make it more affordable. Mr. Obama’s plan would require only children to have coverage; his plan would require employers to provide coverage or contribute to a new public program that would make insurance more affordable to people not covered by their jobs or by the government.

“The only difference between Senator Clinton’s health care plan and mine is that she thinks the problem for people without health care is that nobody has mandated — forced — them to get health care,” Mr. Obama said. “That’s not what I’m seeing around Nevada. What I see are people who would love to have health care. They desperately want it. But the problem is they can’t afford it.”

Many experts in health care agree that without a mandate, some people would not get coverage. The Clinton campaign puts that figure at 15 million people.