Republican efforts in Congress to “repeal and replace” the federal Affordable Care Act are back from the dead. Again.

While the chances for this last-ditch measure appear iffy, many GOP senators are rallying around a proposal by Sens. Lindsey Graham (R-S.C.) and Bill Cassidy (R-La.), along with Sens. Dean Heller (R-Nev.) and Ron Johnson (R-Wis.)

They are racing the clock to round up the needed 50 votes — and there are 52 Senate Republicans.

An earlier attempt to replace the ACA this summer fell just one vote short when Sens. Susan Collins (R-Maine), Lisa Murkowski (R-Alaska) and John McCain (R-Ariz.) voted against it. The latest push is setting off a massive guessing game on Capitol Hill about where the GOP can pick up the needed vote.

After Sept. 30, the end of the current fiscal year, Republicans would need 60 votes ­— which means eight Democrats — to pass any such legislation because special budget rules allowing approval with a simple majority will expire.

Unlike previous GOP repeal-and-replace packages that passed the House and nearly passed the Senate, the Graham-Cassidy proposal would leave in place most of the ACA taxes that generated funding to expand coverage for millions of Americans. The plan would simply give those funds as lump sums to each state. States could do almost whatever they please with them. And the Congressional Budget Office has yet to weigh in on the potential impact of the bill, although earlier estimates of similar provisions suggest premiums would go up and coverage down.

“If you believe repealing and replacing Obamacare is a good idea, this is your best and only chance to make it happen, because everything else has failed,” said Graham in unveiling the bill last week.

Here are five things to know about the latest GOP bill:

1. It would repeal most of the structure of the ACA.

The Graham-Cassidy proposal would eliminate the federal insurance exchange, healthcare.gov, along with the subsidies and tax credits that help people with low and moderate incomes — and small businesses — pay for health insurance and associated health costs. It would eliminate penalties for individuals who fail to obtain health insurance and employers who fail to provide it.

It would eliminate the tax on medical devices.

2. It would eliminate many of the popular insurance protections, including those for people with preexisting conditions, in the health law.

Under the proposal, states could “waive” rules in the law requiring insurers to provide a list of specific “essential health benefits” and mandating that premiums be the same for people regardless of their health status. That would once again expose people with preexisting health conditions to unaffordable or unavailable coverage. Republicans have consistently said they wanted to maintain these protections, which polls have shown to be popular among voters.

3. It would fundamentally restructure the Medicaid program.

Medicaid, the joint-federal health program for low-income people, currently covers more than 70 million Americans. The Graham-Cassidy proposal would end the program’s expansion under the ACA and cap funding overall, and it would redistribute the funds that had provided coverage for millions of new Medicaid enrollees. It seeks to equalize payments among states. States that did not expand Medicaid and were getting fewer federal dollars for the program would receive more money and states that did expand would see large cuts, according to the bill’s own sponsors. For example, Oklahoma would see an 88 percent increase from 2020 to 2026, while Massachusetts would see a 10 percent cut.

The proposal would also bar Planned Parenthood from getting any Medicaid funding for family planning and other reproductive health services for one year, the maximum allowed under budget rules governing this bill.

4. It’s getting mixed reviews from the states.

Sponsors of the proposal hoped for significant support from the nation’s governors as a way to help push the bill through. But, so far, the governors who are publicly supporting the measure, including Scott Walker (R-Wis.) and Doug Ducey (R-Ariz.), are being offset by opponents including Chris Sununu (R-N.H.), John Kasich (R-Ohio) and Bill Walker (I-Alaska).

On Tuesday 10 governors — five Democrats, four Republicans and Walker — sent a letter to Senate leaders urging them to pursue a more bipartisan approach. “Only open, bipartisan approaches can achieve true, lasting reforms,” said the letter.

Bill sponsor Cassidy was even taken to task publicly by his own state’s health secretary. Dr. Rebekah Gee, who was appointed by Louisiana’s Democratic governor, wrote that the bill “uniquely and disproportionately hurts Louisiana due to our recent [Medicaid] expansion and high burden of extreme poverty.”

5. The measure would come to the Senate floor with the most truncated process imaginable.

The Senate is working on its Republican-only plans under a process called “budget reconciliation,” which limits floor debate to 20 hours and prohibits a filibuster. In fact, all the time for floor debate was used up in July, when Republicans failed to advance any of several proposed overhaul plans. Senate Majority Leader Mitch McConnell (R-Ky.) could bring the bill back up anytime, but senators would immediately proceed to votes. Specifically, the next order of business would be a process called “vote-a-rama,” where votes on the bill and amendments can continue, in theory, as long as senators can stay awake to call for them.

Several senators, most notably John McCain, who cast the deciding vote to stop the process in July, have called for “regular order,” in which the bill would first be considered in the relevant committee before coming to the floor. The Senate Finance Committee, which Democrats used to write most of the ACA, has scheduled a hearing for next week. But there is not enough time for full committee consideration and a vote before the end of next week.

Meanwhile, the Congressional Budget Office said in a statement Tuesday that it could come up with an analysis by next week that would determine whether the proposal meets the requirements to be considered under the reconciliation process. But it said that more complicated questions like how many people would lose insurance under the proposal or what would happen to insurance premiums could not be answered “for at least several weeks.”

That has outraged Democrats, who are united in opposition to the measure.

“I don’t know how any senator could go home to their constituents and explain why they voted for a major bill with major consequences to so many of their people without having specific answers about how it would impact their state,” said Senate Minority Leader Chuck Schumer (D-N.Y.) on the Senate floor Tuesday.

Kaiser Health News (KHN) is a national health policy news service. It is an editorially independent program of the Henry J. Kaiser Family Foundation.