WASHINGTON — Republicans are working their way through a list of demands in order to secure enough votes to pass a pared-down version of an Obamacare repeal bill as the Senate prepares for a long night of voting on health care.

In the latest bid to attract votes, House Republican leaders announced that they would agree to a joint negotiation with the Senate to fatten up any bill they pass, satisfying the demands of members who don't want the so-called "skinny" repeal to be the final product.

Sen. Lindsey Graham had particularly harsh language about the effort.

“The skinny bill as policy is a disaster. The skinny bill as a replacement for Obamacare is a fraud. The skinny bill is a vehicle to getting conference to find a replacement,” Graham, R-S.C., said at a Thursday evening news conference with fellow republican Senators John McCain and Ron Johnson and Bill Cassidy.

"Not only do we not replace Obamacare, we politically own the collapse of health care," Graham added. "I would rather get out of the way and let it collapse than have a half-ass approach where it is now our problem. So we are not going to do that with our vote."

The House, reluctant to enter into negotiations with a Senate that has been unable to win the support of 50 Republicans on either a straight repeal of Obamacare or a repeal-and-replace plan, has agreed to enter into negotiations with the Senate. But the deal says that the Senate has to vote for any post-conference legislation first to show they can pass it.

"If moving forward requires a conference committee, that is something the House is willing to do," House Speaker Paul Ryan said in a statement. "The reality, however, is that repealing and replacing Obamacare still ultimately requires the Senate to produce 51 votes for an actual plan."

Ryan moved forward as members of his own conference were rejecting a slimmed-down version of a Senate bill.

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"There’s not enough appetite to take (the Senate bill)," said Rep. Mark Meadows, R-N.C. "Why would you have seven years and seven months to do that? That’s embarrassing."

Republican Senate leaders have scaled back their ambitious goal of completely repealing Obamacare because they couldn’t find agreement among their own members on how to go about it. So now they hope to pass, at some point tonight or tomorrow, the slimmed-down version of repeal.

"At this point we're obviously looking for a vehicle that gets us to conference," said Sen. Pat Toomey, R-Penn., indicating his support.

Others are skeptical.

Sen. Shelley Moore Capito, R-W.Va., said that she's "going to have to see how the process moves forward."

Even the contents of the "skinny" repeal are getting eventhinner.

A repeal of a tax on medical devices, which Republicans had hoped would be in the bill, is not likely to make it because it would violate budget rules, according to sources and Senators involved in negotiations.

The contents of the “skinny” repeal will largely depend on which parts can win the support of 50 Republican senators in Thursday's voting and what fits in the confines of the budget rules which require that the bill has to save at least $133 billion. During their weekly lunch Thursday, Republicans huddled with officials of the CBO to try and piece together a bill that wouldn't violate Senate rules.

The contours of the bill, at this point, include a repeal of the individual mandate to purchase insurance, the defunding of Planned Parenthood, give states more flexibility to opt out of insurance waivers, and a short-term repeal of the employer mandate to provide insurance.

“We just have to get back to work and see what can get 50, 51, or 52 votes,” said Sen. Pat Roberts, R-Kan. “We’re working on that,” adding that Republicans are going “down the laundry list of things we can agree on.”

To reach that “skinny” bill, the Senate on Thursday night will begin what’s called a "Vote-a-Rama," where senators will vote consecutively on as many amendments as they want. Republicans are likely to offer amendments that they’d like to see in a health care bill, but the final package will only include items have the support of at least 50 Republicans.

Related: The Health Care 'Vote-a-Rama' and End Game

Democrats, objecting to the GOP’s process say that they won’t offer any amendments during the "Vote-a-Rama" until Republicans show what they plan to offer in their “skinny” bill.

Democrats also requested an analysis from the non-partisan Congressional Budget Office that found that an additional 16 million people would lose their insurance under the Republicans’ bare-bones bill.

The “skinny” repeal is far from Republicans’ campaign promise of also rolling back the Medicaid expansion, subsidies to help people purchase insurance, taxes, and insurance regulations.

"It was deeply disappointing to see those six Republicans who voted for repeal in 2015 to turn around and vote against it last night," said Tim Phillips, head of the Charles and David Koch-backed Americans for Prosperity.