By all appearances, the Republican health care crusade has already run its course, but tomorrow morning, four GOP senators will make one last-ditch effort to get it back on track.

Sens. Lindsey Graham (R-S.C.), Bill Cassidy (R-La.), Dean Heller (R-Nev.), and Ron Johnson (R-Wis.) will formally unveil the only remaining Republican plan to overhaul the nation’s health care system. For reasons that aren’t altogether clear, they’ll be joined by former Sen. Rick Santorum, who lost his re-election bid in a landslide over a decade ago.

NBC News obtained an advanced draft of the proposal, which has been percolating for a couple of months.

The 23-page summary draft and an explanation of funding, which Graham’s office confirmed is authentic, attempts to achieve parity in federal funding between states that expanded Medicaid and those that did not by 2026. That division was one that helped to kill the Senate’s efforts because senators from expansion states tended to oppose the legislation in its previous versions due to the roll-back of the Medicaid expansion. The bill also provides federal money to states to implement their own health care plan as opposed to one system for all 50 states that exists under Obamacare.

We’ve discussed many of the profound flaws in this plan before, and we can go into more detail once the legislation is available for scrutiny. For now, however, let’s consider whether the Graham-Cassidy plan has a credible chance at success.

After its unveiling tomorrow, the bill will have to receive a score from the Congressional Budget Office, receive committee scrutiny, pass the committee, be subjected to Byrd Rule scrutiny, receive a floor debate, face a series of votes on amendments, and pass the Senate with 50 votes. At that point, the House would have to pass the same bill as-is, or make changes that the Senate would again approve with 50 votes.

In order for the plan to become law, all of this has to happen by Sept. 30 at midnight. In other words, proponents of Graham-Cassidy will have 17 days to get all of this done.

This isn’t to say it’s impossible, but even the most ambitious Republicans should concede this is a steep cliff to climb.

As the process moves forward, there are a few key angles to keep in mind.

First, in theory, this bill will be considered under “regular order,” which means the legislation will have to go through committee, which will take quite a bit of time. If GOP leaders decide to short-circuit the process and bring the bill directly to the floor, senators like John McCain should balk, but whether they’d follow through on their stated principles is unclear.

Second, the relevant committee is the Health, Education, Labor, and Pensions Committee (also known as HELP), which has 23 members – 12 Republicans and 11 Democrats. Among the GOP senators on the panel are Maine’s Susan Collins, Alaska’s Lisa Murkowski, and Kentucky’s Rand Paul. If even one of them opposes the plan in committee, it will fail.

Third, Rand Paul is already expressing opposition to Graham-Cassidy, largely because it keeps so many of the taxes that are already part of the Affordable Care Act. In fact, the Kentucky Republican told reporters yesterday that this plan would “probably” be worse than doing nothing. Of course, Rand Paul made similar noises the last time his party took up health care, but in the end, he voted with his party. What he’ll do this time is unclear.

Fourth, keep an eye on how the conservative movement responds to the developments. If some of the major players – Americans for Prosperity, Heritage Action, Club for Growth – shrug their shoulders and focus on tax reform, GOP leaders will be more likely to let Graham-Cassidy wither on the vine. If, however, they demand the party take the plan seriously, the added pressure may help keep it alive.

Despite all of the reasons for skepticism, I’d warn health care advocates against complacency. Congressional Republicans can move pretty quickly when they have a goal in mind, and it’s not exactly a secret that regressive health care policymaking remains a top GOP priority.

Grassroots activism helped kill the far-right health care crusade once. It may be necessary to do so again.

Postscript: I wonder what would’ve happened if Graham, Cassidy, Heller, and their allies had spent Congress’ summer break cultivating intra-party support for this plan, and had a bill ready to drop the day lawmakers returned to work. I guess we’ll never know.