WASHINGTON, Dec. 14 — Fresh from their victory on Medicare, Congressional Republicans and the Bush administration say they are planning a new initiative to help provide health insurance to people under 65 who have no coverage.
The Senate majority leader, Bill Frist, Republican of Tennessee, is developing legislation and said it would be high on his agenda next year.
Just minutes after President Bush signed the Medicare bill on Dec. 8, Dr. Frist said he was turning his attention to the uninsured.
"For my next three years," he said, "that will be the overriding issue. That's the next big challenge."
Details of the package have not been decided. But members of Congress and administration officials said they were considering several proposals: tax credits to help individuals and families buy health insurance; expanded eligibility for existing health programs; and new tools to help small businesses band together and buy insurance.
Democrats are sure to emphasize the issue in the 2004 elections. The Census Bureau recently reported that the number of people without health insurance shot up last year by 2.4 million, the largest increase in a decade, to 43.6 million. From 2000 to 2002, the number of uninsured rose 9.5 percent, as health costs surged and many workers lost coverage provided by employers.
President Bush fulfilled a campaign promise by adding a drug benefit to Medicare, and Republican pollsters say that with a proposal on the uninsured, he could cement his leadership role in an area of domestic policy long claimed by Democrats.
David H. Winston, president of the Winston Group, a Republican polling firm, said: "Having passed the Medicare law, Republicans will be seen as more credible when they offer proposals on the uninsured. The public is not expecting perfection, but is looking for progress."
Administration officials said Mr. Bush would try to head off Democratic criticism by proposing a major investment in tax credits and other measures for the uninsured.
But prospects in Congress are clouded by lingering Democratic bitterness over the Medicare law. Democratic leaders, shut out of negotiations on Medicare, are in no mood to cooperate with Republicans on another health care issue.
In addition, it will be difficult to find money for a major initiative at a time of large budget deficits. Congress and the administration are looking at proposals that cost $50 billion to $80 billion over 10 years.
Republicans and Democrats have worked together on some initiatives, including a 2002 law that provides tax credits to pay 65 percent of health plan premiums for people who have lost their jobs because of an increase in foreign imports.
Senators Charles E. Grassley, Republican of Iowa, and Max Baucus, Democrat of Montana, recently introduced a bill to extend that tax credit to anyone receiving unemployment compensation. Senators Olympia J. Snowe, Republican of Maine, and Edward M. Kennedy, Democrat of Massachusetts, have introduced a bill that would provide coverage to parents of children who already qualify for Medicaid or the Children's Health Insurance Program.
The major Democratic candidates for president have offered comprehensive proposals to expand health insurance coverage. For example, Senator John Kerry of Massachusetts has outlined a plan to guarantee coverage for virtually all children. Howard Dean, a physician, advocates "a repeal of Bush's tax cuts so that we can provide universal health care," and he points to his record as governor of Vermont, where the proportion of people without insurance is among the lowest in the nation.
Dr. Frist has appointed a group of 10 Republican senators to propose ways of covering the uninsured. The panel, headed by Senator Judd Gregg of New Hampshire, is considering different options for specific segments of the population.
Karen M. Ignagni, president of the American Association of Health Plans, expressed a view that seems to be taking hold in Congress.
"In the last decade," Ms. Ignagni said, "we learned that one size doesn't fit all. The uninsured are a diverse population. Many are working but cannot afford the insurance that's offered to them. Some are working but not offered insurance. Others are temporarily uninsured because they're between jobs. Others fall through the cracks of public programs."
Health economists say that one-fifth of workers who are offered insurance do not take it. A recent study by the Urban Institute estimates that at least half of uninsured children are eligible for a government health insurance program, but not enrolled.
Employers, alarmed at the increase in the number of uninsured, have been lobbying for tax credits and other assistance to make insurance more affordable. They see health benefits as a way to attract and retain workers, and they say they fear that a continued rise in the number of uninsured will increase pressure for national health insurance or other big government programs.
Republicans are divided over proposals to help small businesses band together to buy insurance through their trade associations. In June, the House passed a bill to encourage such "association health plans."
Two members of Dr. Frist's task force, Ms. Snowe and Senator Jim Talent of Missouri, have introduced a similar bill, with strong support from President Bush. "It makes sense to give small businesses the same bargaining power that big companies enjoy," Mr. Bush said.
But another member of the panel, Senator Don Nickles of Oklahoma, opposes the idea, saying it would expose consumers to insurance scams. The association health plans, Mr. Nickles said, would be largely exempt from state regulation and would attract healthier workers, "thereby increasing costs for firms that remain in the traditional insurance market."