“There is no doubt that the way I put that forward unequivocally ended up not being accurate,” Mr. Obama said today.

He said he was thinking of the 95 percent of insured Americans who are covered by group insurance provided by employers, unions, Medicare or Medicaid. He also said he believed that a “grandfather clause” would cover those in the remaining 5 percent who wanted to hang onto current policies even if they were not as good as what is available on the new exchanges.

Those explanations are not likely to be terribly persuasive even to those who liked Mr. Obama and supported health care, but have come to doubt him. His political enemies will scoff at them.