The Senate debate on healthcare provides an insight into a highly contentious issue which is likely to dominate the presidential election of 2008, potentially pitting Senator Clinton against Senator Frist, the only doctor in the Senate.

While Dr. Frist, a likely presidential candidate, signaled his support for the measure, Senator Kennedy issued a blistering critique of the bill, claiming it would reduce coverage for millions, while Mrs. Clinton, who as first lady tried and failed to introduce a socialized universal healthcare system, kept her powder dry on the issue.

The bill, proposed by Senator Enzi, a Republican of Wyoming and chairman of the Senate Health Committee, along with two Republican colleagues, will allow small businesses in different states to band together to buy health insurance for their employees.

Republicans claim the measure will allow small businesses to employ bloc power to lower their healthcare costs. Democrats argue that it will enable employers to shirk legal responsibilities in their home states by purchasing plans in other jurisdictions.

A spokesman for Senate Majority Leader Frist, a Republican of Tennessee and presidential aspirant, said he “does support it,” and that a Congressional Budget Office survey had found that “over one million Americans would likely get healthcare coverage if we passed this bill. It only makes sense to allow small businesses to band together to increase their purchasing power and drive down costs.”

Dr. Frist also believes the Enzi bill will give businesses “choices to buy different kinds of plans that may be less expensive,” the spokesman said. “Many small businesses that currently can’t afford to buy health care for their employees may be able to do so under this bill.”

Prominent Democrats shared the Republicans’ hopes, but not their vision. Mr. Kennedy, a Democrat of Massachusetts, made clear his fierce opposition to the measure, but most of his colleagues were more moderate in their remarks.

“Senator Schumer agrees that we should make health insurance more affordable for small businesses,” a spokesman in his office said, “but he opposes the parts of the Enzi bill that go far beyond small businesses and eliminate important consumer protections for all those covered by health insurance.”

Senator Clinton avoided crossing swords with Republicans over the Enzi bill yesterday, but released a statement on another bill she had introduced with Senator Obama, a Democrat of Illinois, on medical malpractice reform. The statement proposes a system the senator says will “bridge the gap between the medical liability and patient safety systems for the benefit of both patients and physicians.”

The system, she claims, “gives doctors and patients an avenue to find solutions outside of the courtroom, which the vast majority of patients say is what they want,” a wording intended to garner support from tort reformers without upsetting trial lawyers.

Senator Hagel, a Republican of Nebraska, himself a prospective presidential candidate, is “generally supportive” of the Enzi bill, a spokesman said, but thinks it could be improved “with the adoption of some amendments that [he] is currently working on with some of his colleagues.”

Most of the debate surrounding the Enzi bill concerns the actions businesses would take if it were enacted. Will they form large enough blocs to cut the costs of care, as Republicans believe, or simply relieve employers of having to provide it, as Democrats argue?

“Enzi’s bill, if it were to pass, would provide some immediate benefits to a relatively small number of people, primarily those in small firms,” says Joseph Antos of the American Enterprise Institute.

“The major benefits are group rates and eliminating some state mandates that can be very expensive. But once you’ve achieved that, health care costs and premiums will continue to grow very rapidly. In other words, this is not the solution to the health spending crisis.”

Mr. Antos believes the Enzi bill fails to address the underlying issue, the skyrocketing cost of health care, which is growing at a rate of double digits every year.

“The Shadegg bill in the House,” sponsored by the Republican of Arizona, “would do more to make insurance affordable,” said Mr. Antos. “That bill allows insurers to sell plans in any state, not only the state they’re regulated in, allowing individuals to buy plans from any insurer.”

Like the Enzi bill, Mr. Shadegg’s proposal “also would avoid state benefit mandates,” Mr. Antos said. “More importantly, you’re liable to see more aggressive competition among the insurers…[which] is a cleaner way to begin to chip at that very high rate of growth of spending. I believe that kind of a bill would open up the market more widely.”

By a vote of 96-2, the Senate moved yesterday to invoke cloture on the small business health care act, which under Senate procedure limits consideration of the bill to no more than 30 hours before it comes to a vote. GOP Senators Coburn, of Oklahoma, and DeMint, of South Carolina, were the only two to vote against it.