(Bloomberg) -- Senate Republicans are gearing up to try to pass a stripped-down Obamacare repeal plan many hope won’t become law.

Instead -- after going through an all-night session of chaotic amendment votes -- the plan is to get a bill through the Senate and then negotiate with the House on a broader agreement to repeal and replace the Affordable Care Act, a number of Republican senators said Thursday.

"The worst possible outcome is to pass something that most of us believe is a placeholder and it becomes the final product," said Republican Senator Lindsey Graham of South Carolina.

Graham said he would support the measure as long as he gets personal assurances from House Speaker Paul Ryan of Wisconsin that any bill the Senate passes will go to a House-Senate conference committee.

Struggling under their slim 52-48 majority, Republicans say this week’s debate -- including Thursday night’s blizzard of amendment votes known as vote-a-rama -- may ultimately lead to a "skinny" bill that merely ends the mandate that all Americans have insurance or pay a penalty, along with a few other provisions.

‘Long night’

"This is likely to be a very long night," Majority Leader Mitch McConnell on the Senate floor as the chamber started the day’s session. "It will not signal the end of our work, not yet."

Senator John Cornyn of Texas, the No. 2 Republican leader, said Republicans were discussing how many elements of an Obamacare repeal they must include to get enough support to pass.

The House could choose to pass the bare-bones repeal and send it to President Donald Trump, but a number of senators sought to ensure that wouldn’t happen. Ohio’s Rob Portman and other Senate Republicans said they would vote for a "skinny" Obamacare replacement only as a steppingstone to talks with the House, which passed a broader Obamacare overhaul, H.R. 1628, in May.

"I’m for a real replacement" of Obamacare, Portman said.

Senator Roy Blunt of Missouri, a member of the Republican leadership team, said a skinny plan might also eliminate Obamacare’s requirement that most employers offer insurance to their workers, as well as some language allowing states more waivers to modify aspects of Obamacare. He said it is unlikely to include a repeal of a medical device tax that had been under consideration.

Democrats expressed amazement that Senate Republicans would vote for an important piece of health legislation only on condition the House would virtually ignore it.

"This is ridiculous," said Senator Claire McCaskill, a Missouri Democrat. "It’s like we’re in the twilight zone of legislating."

The behind-the-scenes talks contrasted with what was taking place on the Senate floor, where lawmakers were debating whether to replace Obamacare with a broad revision or even repeal it outright.

Early votes underscored the majority party’s difficulty in pushing through a GOP-only bill amid unified Democratic opposition.

The Senate rejected a fuller repeal of Obamacare 45-55 Wednesday. Seven Republicans voted against it, including Senate Health Chairman Lamar Alexander of Tennessee and Senator John McCain, who returned to Washington from his home state of Arizona after a brain-cancer diagnosis to help advance the debate.

Late Tuesday, a 43-57 Senate vote swept aside a revised version of McConnell’s Obamacare replacement, a measure negotiated in secret during weeks of tense GOP talks. Hours earlier, senators barely agreed to start the debate on a 51-50 vote with Vice President Mike Pence casting a tie-breaker after two Republicans defected.

The Senate on Thursday defeated, 0-57, a "Medicare for all" amendment proposed by Republicans even though enacting such a single-payer system is a longtime goal of many Democrats. Independent Senator Bernie Sanders of Vermont -- a single-payer backer -- called the amendment a "sham" that Republicans had no intention of passing.

Bigger challenges await on the Senate floor, including the vote-a-rama, a fusillade of votes on dozens if not hundreds of amendments. Democrats may offer poison pills, and other proposals might divide Republican moderates and conservatives.

CBO estimate

Senate Minority Leader Chuck Schumer of New York warned that the passage of a "skinny repeal" alternative is a gambit to get Senate and House Republicans together in talks on a broader replacement plan.

Schumer’s office put out a Congressional Budget Office estimate of a bill that mirrors Republicans’ description of such a measure -- one that would eliminate the individual and employer mandates, repeal the medical device tax and defund Planned Parenthood. The CBO said such a measure would result in 16 million Americans losing their insurance, compared to the 22 million envisioned under the most recent version of McConnell’s replacement bill.

It’s not certain the splintered Republican caucus would agree to support a pared-back Obamacare repeal. Senator Shelley Moore Capito of West Virginia said she was unsure if she can support such a bill.

A plan to repeal only a few parts of Obamacare isn’t uniformly embraced by the House -- particularly since some senators said they hoped the House would accept it as the most Republicans can do to fulfill their campaign promise to ax Obamacare.

House Freedom Caucus Chairman Mark Meadows of North Carolina said Thursday the House would "absolutely not" send a "skinny repeal" of Obamacare straight to Trump’s desk.

"Going to conference may have some merits; we are discussing that now," Meadows said.

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