WASHINGTON – After rejecting several Medicare prescription drug benefit bills, the Senate struggled Monday with a compromise, endorsed by AARP, that could give both parties political bragging rights before the November election.

Democrats lined up behind a scaled-back plan to help primarily low-income seniors and those facing catastrophic-level pharmacy bills in contrast to the universal coverage they advocated last week.

Whether they could pick up enough Republicans to have the 60 votes needed to pass it was complicated by GOP leaders’ efforts to revive instead, bolstered by $30 billion over 10 years, a privately administered plan that was rejected last week.

“I think we’re in a big mess,” Sen. Orrin Hatch, R-Utah, declared Monday.

The new, scaled-back compromise, estimated to cost $400 billion over 10 years, is likely to emerge on the Senate floor Tuesday, the day Senate Majority Leader Tom Daschle has said he wants to complete work on prescription drugs.

Democrats such as Sen. Edward Kennedy of Massachusetts, who had lobbied for a universal plan to offer benefits to all older Americans, have thrown their support behind the measure.

“It’s a significant down payment, which will help millions of senior citizens who need help the most and protect all senior citizens against catastrophic drug costs,” Kennedy said Monday. Kennedy also serves as chairman of the Senate’s health committee.

But so far, Sen. Gordon Smith, R-Ore., and the author of the plan with Sen. Bob Graham, D-Fla., is the only Republican on board. Smith spent Monday lobbying fellow Republicans for support. It was unclear if he would be successful.

“I don’t think they have the votes and they shouldn’t have the votes,” said Sen. Charles Grassley, R-Iowa.

Grassley, Hatch, Sen. Olympia Snowe of Maine and others want lawmakers to return to a 10-year $370 billion proposal, rejected by the Senate a week ago. They argue that, although less expensive than a $594 billion measure originally offered by Democrats, their plan would offer at least some prescription drug benefits to all seniors.

The group, which have called themselves tripartisan because of the support of a Democrat and the Senate’s lone independent, even offered to buy more support by adding $30 billion to raise the cost of the plan to $400 billion.

Democrats have opposed that plan largely because it uses private insurers to administer the benefit. They want to see a benefit administered by Medicare.

The debate exhibited the frenzy of both parties to craft a Medicare bill before Friday’s adjournment for summer recess. Both sides want to appeal to elderly voters, who participate disproportionately in midterm elections.

Some lawmakers seemed to urge caution. “There’s no reason for us to be in any kind of high-noon showdown on prescription drugs,” said Snowe. “We’re in a difficult time frame here.”

The Graham-Smith plan would call for older people with incomes below 150 percent of the federal poverty level to get full drug coverage with nominal co-payments of around $1 to $3.

All others would receive government help of at least 5 percent of the cost of each prescription drug, with more government help available once a patient reached $4,000 in drug costs.