At least a handful of Republican senators will fight to repeal Obamacare until the last possible moment. They have less than three weeks.

The path forward is improbably narrow. Almost every seasoned Washington observer believes it can’t be done. But it’s not totally impossible.

Sens. Bill Cassidy (R-LA) and Lindsey Graham (R-SC) have unveiled the latest version of their health care bill this week. It is a last hope of sorts for Republicans to pass a bill to repeal and replace Obamacare; they have until the end of September to pass the bill using the special budget procedure that allows the legislation to advance without any Democratic votes.

After the cataclysmic failure by Senate Republicans to pass a health care bill in late July, the repeal dream seemed over. Senate Republican leaders signaled they were moving on to tax reform. House Speaker Paul Ryan is also all tax reform all the time. Bipartisan talks have gotten underway for a narrow bill to help stabilize, not roll back, the health care law. President Donald Trump still wants to see repeal, but his attention is often elsewhere.

But despite those headwinds, Cassidy and Graham have pulled together a final iteration of their proposal.

The bottom line is cuts to federal health care spending, in the name of more state flexibility. On its face, this new legislation would encounter many of the same problems that earlier Republican health care bills did: Medicaid cuts and coverage losses. No other plan could get 50 Republican votes. Is this really the one that will?

But nothing motivates lawmakers like a deadline. That’s the best hope that Cassidy-Graham has.

“If you believe repealing Obamacare is a good idea, this is your best and only chance to make it happen because everything else has failed,” Graham said Wednesday.

The odds are stacked against it. The window is small, few other Republicans seem particularly interested in revisiting health care, and the actual policy of the bill still needs to be litigated. Senators haven’t even had a chance yet to unpack how the bill’s complex funding formula would impact their specific states.

“No Senate GOPer will say anything negative about the bill because in concept, sure, more state flexibility is a good thing,” one health insurance lobbyist told me. “But the moment the bill is real and there are funding formulas to fight over, the whole thing will fall apart quickly”

But, hey, it could happen. The Obamacare repeal debate so far has taught us that nothing can be ruled out. This is, after all, the GOP’s last chance.

Just don’t bet on it.

Cassidy-Graham is maybe the most radical Obamacare repeal yet

Vox’s Sarah Kliff explained an earlier version of the bill — not much has changed — in great detail. She summarized its impact this way:

Cassidy-Graham would arguably be more disruptive, not less, to the current health care system. It would let money currently spent on health insurance go toward other programs, providing no guarantee that the Affordable Care Act programs individuals rely on today would continue into the future.

Obamacare’s individual mandate would be repealed, as would some of the law’s taxes. But the foundation of the plan would be a block grant formula that would give each state a set amount of money to spend on their own health care programs, based on how much they would receive under Obamacare. Very few strings would be attached.

That bill’s formula is complex, and policy experts are still untangling its exact consequences. But the general result would be less federal spending than under Obamacare, with the distribution of the funding that remains being shifted from states that expanded Medicaid to states that choose not to.

“It’s reallocating a smaller pot of money, and some of that money is going from states that expanded Medicaid and going to states that didn’t,” Chris Sloan at Avalere Health, an independent consulting firm, told me.

Cassidy-Graham would also fundamentally overhaul Medicaid, placing a federal spending cap on the insurance program, which covers 75 million Americans, for the first time.

The bill’s spending would also expire after 2026, meaning this huge swath of federal health care funding would end barring further action by Congress. The sum result would be as many as 20 million fewer people having insurance, per some preliminary estimates from outside experts.

“The ballgame here is the money. If states have a lot less money to play with than under the current system, it's inevitable that fewer people will be covered,” said Larry Levitt, senior vice president at the Kaiser Family Foundation.

Everything must go perfectly for the bill to pass the Senate in time

The September 30 deadline is the first hurdle. Cassidy laid out his ideal timeline to Bloomberg’s Steve Dennis:

Cassidy timeline to revive partial ACA repeal: Text by Monday, 2 weeks for CBO, 5 days to pass Senate/House Sept. 30. — Steven Dennis (@StevenTDennis) September 7, 2017

The text came out this week. The Congressional Budget Office must analyze it, a process that precedent has shown could take two weeks or more. Then the Senate’s parliamentarian must review it to make sure it complies with the rules for legislation considered under budget reconciliation, the special process that the Senate has used to try to advance a repeal bill with only 51 votes rather than the usual 60.

That will all take time. Further complicating that schedule are some swing votes, like Sen. John McCain (R-AZ), who have at times conditioned their support on the bill going through regular order.

So some time might have to be found for committee hearings, too, all in a matter of days while the Senate is considering a defense spending bill and other urgent business like reauthorizing the Federal Aviation Administration.

As Cassidy has sketched out, though, the timeline could maybe work, at least mechanically, if there are no hiccups along the way. It helps that the government spending bill and a debt limit increase have been cleared from the schedule, after Trump struck a deal with Democratic leaders.

But the fundamental problem for Obamacare repeal in the Senate has been the extraordinarily thin margin for error. There are 52 Senate Republicans, and 50 of them must vote for any bill to pass. The deep divides within the GOP over health policy have made it impossible to find a plan that can win 50 votes so far.

Senate leadership couldn’t do it. Now the task is being undertaken by Cassidy and Graham, neither of whom have even the perch of a relevant committee chairmanship. Senate leaders seem totally unwilling to risk yet another embarrassment by publicly embracing the plan. They are talking up tax reform as often as they can.

So Cassidy and Graham seem to be on their own in marshaling support, and there is likely no way Senate Majority Leader Mitch McConnell would put the bill up for a vote without being absolutely sure it would pass.

“McConnell has zero interest in presiding over another goat rodeo,” a second health care lobbyist told me.

But here again, while the odds are very long, it isn’t totally inconceivable that the duo could find the support they need. The final Obamacare repeal bill that the Senate voted on in late July — so-called “skinny” repeal — got 49 votes. Only McCain and Sens. Lisa Murkowski (R-AK) and Susan Collins (R-ME) voted against it.

If those 49 Republicans support Cassidy-Graham, too, and one of those three — probably McCain, who has expressed some general support for the concept in the past — were to flip, then the bill could get to 50. Vice President Mike Pence could break a 50-50 tie.

It’s a tall order. Twenty Senate Republicans represent states that expanded Medicaid, which would be most disadvantaged by Cassidy-Graham’s funding formula. It’s not at all clear that conservatives like Sen. Ran Paul would support a bill that still spends $1 trillion on health care but doesn’t technically undo any of its top insurance regulations.

Rand Paul tells reporters he opposes both Graham Cassidy and the HELP stabilization effort — Peter Sullivan (@PeterSullivan4) September 11, 2017

Without Paul, Cassidy and Graham must win over either Collins or Murkowski, the two Senate Republicans who have opposed every iteration of Obamacare repeal so far.

Nevertheless, if you squint, you could see the theoretical path to success: The bill moves along briskly over the next three weeks and 50 Senate Republicans — all of whom have already voted for one version of repeal or another — decide to support their last chance to fulfill a seven-year promise to undo Obamacare. The House accepts that this is the best the Senate can do and passes it. Trump signs it because he wants a win.

But that would mean the bill hits absolutely no snags, after an eight-month Obamacare repeal debate that proved perilous and painful for Republicans.

All this explains the underlying skepticism in Washington. Few Republicans want to publicly kill Cassidy-Graham because Obamacare repeal is still the party line. But it’s incredibly difficult to see how this plan could succeed where the others have failed.

“They don’t want to be the one to throw cold water on it now. They just want it to go away,” the insurance lobbyist said. “Bottom line: Outside of Trump, Graham, and Cassidy, nobody thinks this is real.”