After hours of debate and a failed vote on single-payer healthcare Thursday, the Senate is slated to begin a marathon voting session Thursday night before Republicans attempt to pass a slimmed down of version of their Affordable Care Act repeal bill.

The Senate will first begin its so-called vote-a-rama, a grueling process tied to budget reconciliation in which all senators vote on a series of back-to-back amendments that could last 10 hours. There is no time limit on introducing amendments, and Sen. Chris Murphy (D-Conn.) has vowed to introduce 100.

Senators already saw one amendment to the Better Care Reconciliation Act on Thursday. The amendment, introduced by Sen. David Daines (R-Mont.) called for the adoption of a single-payer healthcare system. While Daines said he did not support the amendment, the vote was an attempt to get Democrat senators to go on the record with their views on the controversial issue.

The amendment failed with 57 Senators voting against, zero in favor and 43 voting “present.”

After the marathon voting session, senators will likely take up a skinny version of Senate Republicans’ repeal bill, which would preserve the subsidies to buy health insurance and the Medicaid expansion and most of the taxes that pay for it, but would get rid of the individual and employer mandate. The nonpartisan Congressional Budget Office determined that such a bill would lead to 16 million more uninsured individuals by 2021.

The “skinny repeal” comes Senate Republicans’ other bill attempts failed, including a straight repeal of the ACA without a replacement. If Senate Republicans manage to pass a skinny repeal bill that leaves most of Obamacare in place, a House-Senate conference committee would hash out a compromise, which could take months.

“One of the promises our Republican friends have made over and over again was to bring down premiums, but skinny repeal would break that promise,” Senate Minority Leader Chuck Schumer (D-NY) said during debate Thursday. The bill, he added, is “a recipe for disaster” and a “shameful way of legislating.”

But Sen. Lamar Alexander (R-Tenn.) said that while the skinny repeal is not a solution for Obamacare, it is a way to get to a place where a solution can be written.

Insurance industry lobbying group America’s Health Insurance Plans also came out against a skinny repeal on Thursday, warning that such proposal would boost premiums, reduce consumer choice and ultimately lead to an increase in the uninsured. Several other insurers have warned that axing the mandate without putting an adequate subsitute in place would further destabilize the individual insurance market.

Senate Republicans this week ran into several new roadblocks on their quest to repeal the ACA. One came earlier Thursday when the Senate parliamentarian ruled that Republicans’ plan to allow states to waive certain Affordable Care Act requirements would violate Senate budget rules, according to Senate Budget Committee Democrats. That decision prevents GOP leadership from passing a bill with a straight 51-vote majority.

The key provision of the Better Care Reconciliation Act that would have amended Section 1332 of the ACA to allow states to waive certain rules—such as the essential health benefits and pre-existing condition requirements, as long as the proposal didn’t increase the federal deficit—violates the so-called Byrd rule, MacDonough determined.

The Byrd rule allows for any bill moving along the budget reconciliation process, like the Senate healthcare bill, to be blocked for containing provisions that aren’t directly related to the federal budget. Now the provision would need 60 votes to pass, which would require the support of Democrats who oppose the overall GOP legislation.

Earlier this week, MacDonough ruled that a measure in the bill to allow individual-market insurers to charge older people premiums five times higher than younger people cannot be passed under Senate budget reconciliation rules. The ACA only allows insurers to charge older customers three times as much.

She also held that the bill’s provision allowing small businesses to band together across state lines to establish association health plans that are exempt from state regulation did not meet reconciliation rules. Last week, MacDonough held that a number of other key provisions did not comply with reconciliation rules. Those include prohibitions on Medicaid funding for Planned Parenthood for one year and on abortion coverage under health plans purchased with premium tax credits.