"All we need is one vote and we can change America for the better," Mr. Clinton said in a speech to health care professionals at the University of Missouri.
Mr. Clinton chose to bring the issue to Missouri, where Democratic Gov. Mel Carnahan is trying to unseat Sen. John Ashcroft, R-Mo. Mr. Clinton applauded a state patients' bill of rights backed by Carnahan and signed into law in 1997.
Attacking the measure Republicans pushed through the Senate, Mr. Clinton said an analysis by experts at George Washington and Rutgers universities concludes that the Republican measure would be "far worse than were Congress to enact no measure at all."
According to the analysis, the Senate bill would leave more than 135 million Americans without the guarantee of full protection, fail to guarantee access to health care specialists and allow health plans to subject patients to financial penalties when they seek emergency care.
"The Senate bill allows plans to saddle patients with an extra charge if they don't first call their health plan for permission before they go to an emergency room," Mr. Clinton said.
The Republican bill would guarantee access to emergency room care, out-of-network physicians and specialists for an estimated 56 million insured individuals. Patients also would be permitted to file suit in federal court against HMOs that improperly denied care, but only after an independent reviewer said the HMO erred in denying care or coverage.
Republicans said the lawsuit provision would apply to 131 million insured people who could seek unlimited economic damages and up to $350,000 in compensatory damages. Punitive damages would be barred, as would class-action lawsuits.
In June, Senate Democrats forced a vote on their version of a patients' bill of rights. It failed 51-48. But one Democrat did not vote, and if he had voted to support the bill, it would have come within one vote of a tie, which Vice President Al Gore, as president of the Senate, could break.
A bill that passed the House last year would cover an estimated 161 million people, granting many of the same basic protections provided by the Senate bill. But it would allow patients to sue in both state and federal courts with no limit on the amount of damage awards.
Mark Atkins, 33, of Columbia, called Mr. Clinton's approach to health care "socialist."
"The federal government has no stinking business in health care of any kind," said Atkins, who held a sign that read, "Socialists are people too. They're just not Americans."