Republicans have 10 days left to unite behind yet another push to repeal Obamacare — and the Senate is only in session for five of those days.

So far, there still aren’t enough Republican votes behind the latest Obamacare repeal-and-replace proposal — a plan from Sens. Lindsey Graham (SC) and Bill Cassidy (LA) that would block-grant existing Obamacare funding, cap federal health care spending, and send it down to the states to create their own health care programs. In effect, analysts say the proposal would cut $215 billion in federal health care funding to states.

And there are several procedural hurdles Republicans will have to jump to get this done. In less than a week, Republicans will have to get a score from the Congressional Budget Office and run the proposal past the Senate parliamentarian, who will decide whether this health plan adheres to Senate rules. Already there are hints that Graham-Cassidy could see some pretty substantial changes after that process — which could put more votes at risk.

Even so, the Senate is positioning itself to get this done. Senate Republicans’ efforts to ramp up momentum behind the last Obamacare repeal bill left standing has largely seen some success.

On Tuesday, Vice President Mike Pence and Seema Verma, the Centers for Medicare and Medicaid Services administrator, joined Senate Republicans at lunch to lobby for Graham-Cassidy’s passage. President Trump has voiced his support, and Senate leadership has taken a more active role in whipping the proposal’s vote count. A top committee chair proposed a last-minute hearing to give the bill the appearance of some regular congressional order.

If the Senate manages to pass the proposal by September 30, then Graham-Cassidy will still need to go back to the House — where it can no longer be amended. In other words, the Senate needs to be able to pass a version of Graham-Cassidy that the lower chamber will take as is. Already some House members from blue states, who would see the most drastic cuts, have raised concerns. If they all say no, there’s no going back to the drawing board on Graham-Cassidy.

None of this will be easy. But as Vox’s Sarah Kliff has written, it’s looking more and more real. Here’s a rundown of the procedural roadblocks that lie ahead.

Senate Republicans’ Obamacare repeal checklist

Like last time, Republicans are planning to repeal Obamacare through budget reconciliation, a process that allows the Senate to pass legislation without the threat of the Democratic filibuster.

But “budget reconciliation” bills are restricted in what they are able to do — namely, they have to somehow impact federal spending, whether through revenue or spending. They also have to achieve a level of savings overall, and have a hard deadline to get all this done: September 30.

Republicans have fewer than seven working days to pass Obamacare repeal

If Republicans don’t pass Graham-Cassidy by September 30, the end of the fiscal year, they will no long be able use “budget reconciliation” — meaning anything they pass on health care will have to be done on a bipartisan basis, with eight Democrats on board in the Senate.

And Democrats, who have begun some talks on a bill that would stabilize Obamacare’s markets, have made it clear they’re not interested in repealing their signature health care legislation.

This has created a very tight schedule for Republicans — and is putting the many senators who decried a lack of transparency and regular order in the past Obamacare repeal debates in a difficult position.

When Sen. John McCain (R-AZ) was the deciding vote tanking the Republicans’ last push for repeal, he said he wanted negotiations to be bipartisan and to go through a public and thorough hearing process. The sentiment was echoed by many, including the chair of the Senate Health, Education, Labor, and Pensions Committee, Sen. Lamar Alexander (R-TN), who was working on a bipartisan health care proposal with Democrat Sen. Patty Murray (D-WA) to stabilize Obamacare, until Republicans walked away from negotiations early this week.

It will be hard to make the case that this bill went through a thorough debate process under regular order with only a week to pass it. But Republicans are making an effort to make a show of it. For one, the text of this proposal has been out much longer than past iterations of the Obamacare repeal bills.

They are quick to say the plan wasn’t written by Senate leadership, and the Senate Finance Committee will hold a hearing on Monday to debate the Graham-Cassidy-Heller-Johnson proposal.

This proposal still needs a score from the Congressional Budget Office

Graham-Cassidy has not yet received an official score from the Congressional Budget Office, the nonpartisan body that analyzes the cost and coverage of bills.

Outside analysts expect this bill will lead to millions of Americans losing coverage compared with the existing health law — similar to past iterations of the Republican-led repeal efforts.

Cassidy has long expressed that he disagrees with the CBO’s analyses on health care, saying their fundamental model is based on the individual mandate — a provision in Obamacare that taxed Americans for choosing to remain uninsured. Sen. Ron Johnson (R-WI), who is a co-sponsor of Graham-Cassidy, has repeatedly said there is no need for more information from the CBO.

"I think we can pretty well decide based on the information we already have," he said.

But Republicans’ gripes over the CBO score aside, the Senate will still need a score before they vote, in order to know how the bill impacts the deficit — a requirement under budget reconciliation.

So far, the CBO has said it cannot release a full report as early as next week but will try to provide as much bare-bones analysis as it can — which Republicans can use to vote if it comes to it. Pence said they were "lighting a fire" under the CBO to get this done in time.

"We've been assured that we'll have a score ... by the 25th," he said.

This bill will have to survive the Byrd Rule

The Senate parliamentarian will also have to make sure this bill is compliant with the Byrd Rule, which is supposed to limit budget reconciliation legislation to items affecting federal revenue or spending.

As with Republicans’ previous Obamacare repeal proposals, Graham-Cassidy includes several measures that could be gutted from the final bill. While the parliamentarian has yet to make a ruling on Graham-Cassidy, past Obamacare repeal rulings give an early indication that some provisions, like abortion restrictions or allowing states to receive waivers from Obamacare-era coverage requirements, could be stripped from the bill.

If provisions like the state waivers are removed from the bill, it could hurt conservative support. As is, conservative Sens. Ted Cruz (R-TX) and Mike Lee (R-UT) seem to be responding positively to this bill, without definitely giving their support. Cruz has already said he is in talks for an amendment that would give states more flexibility on Obamacare regulations.

After September 30, the House has to sign on to whatever the Senate passes

Graham says he has House Speaker Paul Ryan’s assurance that if the Senate gets this done, the House will pass it too. Ryan has called the proposal "our best, last chance to get repeal and replace done."

The pressure is on: After September 30, the House will only be given a yes-no vote on Obamacare repeal. They can’t change the bill, because the budget reconciliation instructions already would have expired in the Senate — meaning the upper chamber would then need to meet an almost certainly impossible 60-vote threshold to pass an amended version. The House isn’t beholden to the September 30 deadline like the Senate is, but their hands are tied on the actual legislation.

As the Washington Post’s Mike DeBonis wrote, this proposal is not a slam-dunk in the House. On both sides of the ideological spectrum, House members have concerns. House conservatives on board with the proposal, for now, are looking toward Graham-Cassidy’s state waivers.

“Having real flexibility for governors and states to provide health care coverage with lower premiums is a critical component for any conservative support,” Rep. Mark Meadows (R-NC), who chairs the House’s archconservative Freedom Caucus, told Vox. Though he isn’t confident those measures will be kept in after the proposal is reviewed by the parliamentarian.

“I have learned to never be confident on anything that had to pass Senate rules or procedures,” he said.

But for conservatives, the threat of a “binary choice” — that it’s this or Obamacare — is a more compelling reason to vote for Graham-Cassidy than it is for the party’s moderates, particularly those from largely Democratic states that would see the largest funding cuts under this proposal.

Rep. Pete King (R-NY) has already said this proposal would be worse than Obamacare for his state. “Right now, I don’t see how I could vote for it. … It’s extremely damaging to New York,” he said.

Another New York Republican, Rep. Tom Reed, voiced similar concerns, calling back to an amendment from his fellow New York Reps. Chris Collins and John Faso, known as the “Buffalo Buyout,” during the House’s Obamacare repeal debate back in March, which made Medicaid cuts more tenable for the state’s counties.

“We are waiting to see if this in fact comes out of the Senate,” he said. “I would be concerned that the Faso-Collins amendment, which is critically important for New Yorkers, isn’t included. But to be honest, I’m not overly optimistic the Senate will move this forward.”

California Republicans will have to make the same calculus: whether party pressure to once and for all repeal Obamacare will supersede what could be a devastating policy for their states.