WASHINGTON - Despite an overwhelming show of support for helping older Americans buy prescription drugs, the Senate blocked competing plans yesterday that would add that benefit to Medicare, the government health program for seniors.

In a series of staged votes on the high-profile issue, Senate Democrats and Republicans put themselves on record as endorsing separate prescription drug plans. But neither party could muster the support needed to gain approval for its plan.

Deep divisions over how to structure the costly new benefit - viewed as one of the central issues in the November election - are frustrating efforts to reach a bipartisan compromise this year.

Negotiators from both sides plan to meet behind closed doors today to discuss a compromise. Because the Republican-controlled House has already approved a GOP plan, Democrats are worried about the political consequences if the Senate fails to act.

"Not only is it extremely important for the seniors of this country, but it's also politically imperative that we do it," said Sen. James M. Jeffords, a Vermont independent who voted in favor of both versions yesterday.

Republican Sen. Charles E. Grassley of Iowa, a main sponsor of his party's Medicare drug plan, said: "Apparently, the Democratic leadership is not interested in making things happen for our seniors. The other side did not want a real debate. They wanted a real issue instead."

But Sen. Edward M. Kennedy, a Massachusetts Democrat, called the Republican proposal "little more than a political fig leaf for the elections."

With control of Congress up for grabs in the midterm election, the conflict over prescription drugs is particularly intense this year. Both parties are eager to capture the support of seniors - who vote in disproportionate numbers and who, polls show, are increasingly concerned about the rising cost of prescription drugs.

Both sides tried to paint yesterday's action not as the collapse of this year's Medicare drug debate but as a necessary step in the process of negotiating a bipartisan solution.

Sen. Bob Graham, a Florida Democrat who is the chief architect of his party's drug coverage proposal, said the votes should be interpreted "not as a signal of defeat, and to go into retreat, but as a call to action."

But the action on the competing drug plans pointed up the wide gulf that separates the parties, one that many say is simply too wide.

Democrats are demanding that the government guarantee drug coverage to seniors, while Republicans advocate plans that would rely in part on private industry to help seniors defray the fast-growing cost of prescription drugs.

Costs of compromise

"The differences between the Democratic and the Republican approaches are so substantial that it's very hard to bridge those differences in an election year," said Ron Pollack, executive director of the group Families USA, which backs the Democratic proposal.

The political costs of a compromise may indeed be too high for both parties at the moment.

Democrats contend that they have an advantage on the prescription drug issue, because voters traditionally trust them more to protect government benefits.

"While Republicans are doing their best to give themselves some political cover on the issue, it's absolutely clear that the public understands who's on their side on this point," said Jim Jordan, executive director of the Democratic Senatorial Campaign Committee. "If voters see ads and become confused on an issue, they will simply fall back on their instinctive and visceral impressions."

But Republicans say their strategy of going head to head with Democrats and offering competing prescription drug plans has worked.

"It's the Democrats who are going to have trouble explaining this, because they've been talking about delivering this for a long time, and they can't," said Dan Allen a spokesman for the National Republican Senatorial Committee. "When we're talking across the country, we're saying, 'We have come to the table and offered a plan and passed a plan.'"

A senior Senate Republican aide put the matter bluntly: "If it's health care, and we're not getting completely killed, we're winning."

Both plans defeated

The Senate essentially rejected both plans yesterday, because neither side could gain the 60 votes necessary to overcome procedural objections under Senate rules. The Democratic measure fell eight votes short, by a margin of 52-47. The Republican plan fell on a vote of 48-51.

The Democratic proposal, sponsored by Graham, Zell Miller of Georgia and Kennedy, would create a new benefit under Medicare that would cover prescription drugs for seniors for a monthly premium of $25, with co-payments of $10 to $40 for most prescriptions.

Republican leaders say the plan would jeopardize the future of Medicare because it is far too costly.

The Republican alternative, sponsored by Grassley, Jeffords and Sen. John B. Breaux, a Louisiana Democrat, would provide drug coverage in one of three ways: under Medicare, through a Medicare managed health care plan or through a drugs-only insurance policy subsidized by the government.

Monthly premiums would average $24 and beneficiaries would have a $250 deductible for the plans, which would cover half of seniors' annual drug costs up to $3,450. It would not cover drug costs above that limit until beneficiaries had spent $3,700, after which the government would pay 90 percent of additional costs.

Democrats decry the Republican plan as stingy, inconsistent and unreliable.

"Their plan is not affordable, not adequate and not Medicare," Kennedy said.

The Republican proposal resembles one passed narrowly last month by the House. It would give private insurers flexibility to design prescription coverage for seniors.

'A wide-open field'

Senate centrists from both parties have been working for weeks to bring the two sides together. Today's talks are expected to focus on a proposal that would let private companies assume the risk for the new prescription drug benefit, with Medicare as a backup.

"There's a wide-open field," said Senate Majority Leader Tom Daschle, a South Dakota Democrat, when asked about the prospects for compromise.

"I'm not going to bet the farm on it, but I think there is a reasonable prospect" for compromise, Graham said.

But aides to top Democrats say privately that most in their party would never support such a model.

Claiming credit

Meanwhile, lawmakers in both parties are preparing to claim credit for making progress on prescription drug issues this year, even if negotiations fail as expected.

Democrats hope to say they are making headway by gaining Senate approval of a measure sponsored by Sens. Charles E. Schumer, a New York Democrat, and John McCain, an Arizona Republican. It aims to increase the use of lower-cost generic drugs by limiting the ability of pharmaceutical companies to use patent laws to keep generics off the market.

Democrats also point to a measure passed by the Senate last week that would allow American pharmacies to reimport less expensive U.S.-made drugs from Canada.

"We're going to do everything in our power to get a prescription drug bill," said Sen. Debbie Stabenow, a Michigan Democrat. But the other measures are "very, very meaningful."