WASHINGTON — Battered by repeated failures to repeal or replace “Obamacare,” Senate GOP leaders retreated to a narrow approach Thursday that would undo just a few of the most unpopular elements of Barack Obama’s law. Democrats vowed opposition as the Senate prepared for a bizarre Capitol Hill ritual, a “vote-a-rama” on amendments that promised to last into the wee hours of Friday morning.

The “skinny repeal” they were considering was being touted as a way for Republicans to get something, anything, out of the Senate after frittering away the first six months of Donald Trump’s presidency trying unsuccessfully to abolish the current law. Talks with the House would follow, with the aim of crafting a compromise repeal-and-replace bill that could pass both chambers sometime in the fall.

Whether Republicans can make it that far looks iffy at best. But Trump tweeted his encouragement, albeit with an ominous touch: “Come on Republican Senators, you can do it on Healthcare. After 7 years, this is your chance to shine! Don’t let the American people down!”

The “skinny bill” strategy emerged after Republicans barely succeeded earlier this week in opening debate on health legislation in the narrowly divided Senate, winning the procedural vote to do so thanks only to Vice President Mike Pence breaking a 50-50 tie.

Hours of debate followed, as well as a few amendment votes that starkly revealed Republican divides. On Tuesday, on a 57-43 vote with nine GOP defections, the Senate rejected a wide-ranging proposal by Majority Leader Mitch McConnell to erase and replace much of the Affordable Care Act. Then on Wednesday, a straightforward repeal measure failed 55-45 with seven Republicans joining Democrats in voting “no,” even though nearly identical legislation had passed Congress two years earlier.

That left Republican senators hunting for other options, and the skinny repeal rose to the top. The measure has not been finalized, but senators have said it could eliminate Obamacare’s two mandates — for individuals to carry insurance and for employers to offer it.

Lobbyists said Republicans were also planning to include a one-year ban on federal payments to Planned Parenthood, extra money for community health centers and waivers for states to permit insurers to sell policies with far narrower coverage than current law allows.

But leaders were encountering problems. The Senate parliamentarian advised that the waiver language violates chamber rules, meaning Democrats could block it. And plans to eliminate Obama’s medical device tax could be abandoned because Republicans need that money for their package.

“It is being called a skinny bill because it won’t have much in it,” said Sen. Lamar Alexander, R-Tenn. “It is not a solution to the Affordable Care Act problems. But it is a solution on how we can get to a place where we can write a solution to the Affordable Care Act.”