Much of the plan is familiar. But the new Cassidy-Graham bill, the latest Republican effort to repeal and replace the Affordable Care Act (ACA), will come with an extra dose of drama and intrigue.

Prior bills to repeal Obamacare, as the ACA is known, went down in flames after the Congressional Budget Office published its official score of the plan—a nonpartisan estimate of how much the bill would cost or save, along with its effect on the number of uninsured Americans and on typical insurance premiums. The Better Care Reconciliation Act, for instance, would have saved the government $321 billion over 10 years, but left 22 million additional people uninsured. The Senate failed to come up with 50 Republicans votes for the measure this summer, and no Democrats supported it.

For the Cassidy-Graham bill, named after Republican Senators Bill Cassidy of Louisiana and Lindsay Graham of South Carolina, senators will have to vote before they even have numbers from the CBO. To pass the measure with a simple majority of 51 votes, the Senate must abide by certain rules and vote by September 30, which is the end of the government’s fiscal year. After that, it will take 60 votes to pass the bill, because the Senate’s filibuster rule will go into effect. There’s no chance the bill will get 60 votes, and the CBO says it can only provide a few rough numbers by Sept. 30. The bill didn’t come out until September 13, and it normally takes the CBO several weeks to complete analysis on complex health legislation. So senators will be voting on a bill without knowing its likely effect on the federal budget or how many people would lose health care coverage under the bill.

It is fairly clear that, like other GOP repeal-and-replace plans, Cassidy-Graham would cut federal payments to Medicaid and drive up the number of uninsured. It would end most major provisions of Obamacare and replace them with block grants states can use to help cover lower-income residents currently insured under the ACA. But funding under Cassidy-Graham would be less generous than the ACA, so the most important question seems to be whether it would leave even more uninsured than earlier GOP plans, or end up a bit more generous.

The CBO won’t report back until October, so Republican Senators will have to decide whether to vote for a bill with incomplete information and even less public airing than two earlier attempts this year to kill the ACA. Expect it to go down to the wire like the BCRA did over the summer. The GOP can only afford to lose two votes, and Sen. Rand Paul of Kentucky has already said he’s out. Pressure will intensify on familiar moderates Susan Collins of Maine and Lisa Murkowski of Alaska. And John McCain, whose no vote doomed the BCRA, could turn out to be the do-or-die vote once again—with less information than he had before.

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Rick Newman is the author of four books, including Rebounders: How Winners Pivot from Setback to Success. Follow him on Twitter: @rickjnewman