The long, halting slog toward Obamacare repeal is set to reach a significant milestone Tuesday, when the Senate is scheduled to vote on ... something.

No, not ”something terrific,” as President Donald Trump promised on the campaign trail. Just ... something. The American public will find out what that something is at about the same time as the Republican senators who Majority Leader Mitch McConnell (R-Ky.) wants to amble down to the well of the Senate, raise their index fingers and say, “Yea.”

Tuesday morning, the Senate is scheduled to begin floor debate on whatever that something is. McConnell is asking GOP senators to approve a procedural motion on a House-passed health care bill, which will then allow him to bring up something else, after which senators will debate and vote on amendments to the something.

No one knows what they’ll be voting to debate. Seriously.

In their zeal to repeal the Affordable Care Act, Senate Republicans have neglected to actually figure out what they want to enact in its stead. More than 40 of them have shown no signs they have any problem with this, and the handful who have wrung their hands in public about it have failed to take the crucial next step of actually coming out against it. Sen. Susan Collins (R-Maine) is the lone exception.

The lives of tens of millions of people and the health care system itself are in the hands of senators who are practically flying blind. And all of this is in the service of legislation that violates Trump’s promises of lower premiums, smaller deductibles, and coverage for everyone. What’s more, polling consistently shows that very few Americans actually want Congress to do any of this.

Just days ago, enough Republican senators had declared they wouldn’t vote on this “motion to proceed” that the effort to repeal the central components of the Affordable Care Act and “replace” them with more meager reforms looked like it might be dead. McConnell pulled the hastily assembled Better Care Reconciliation Act.

But the process showed new signs of life because of pressure from Trump and conservative activists and donors. Another key factor is the lack of conviction among those “moderate” senators who had expressed alarm at the legislation’s massive cuts to federal health care programs, especially Medicaid, but don’t want to be known as the Republicans who killed Obamacare repeal.

Nevertheless, it’s not clear whether McConnell has the 50 votes he needs to move forward, especially with Sen. John McCain (R-Ariz) likely unavailable after being diagnosed with brain cancer.

So, what will happen in the Senate this week?

This bill

McConnell could bring up a version of the Better Care Reconciliation Act, his favored Obamacare “replacement.”

This bill would slash federal Medicaid funding by more than one-quarter, severely weaken the Affordable Care Act’s protections for people with pre-existing conditions; shrink financial assistance for people who buy private health insurance and make it available to fewer people; permit health insurance companies to go back to selling skimpy, junk policies that cover fewer things; and increase costs for older, sicker people in order to allow younger, healthier people to buy insurance with even bigger deductibles than found on the Obamacare exchanges.

This bill would increase the number of Americans without health coverage by 22 million, bringing the total to 50 million in 2026, compared to 28 million if the Affordable Care Act were left in place, the Congressional Budget Office reported Thursday.

That bill

Or McConnell could opt to bring up the Obamacare Repeal Reconciliation Act. Unlike the other bill, this one is all repeal and no replace. Congress passed a version of this bill in 2015, and President Barack Obama vetoed it.

The legislation would take away funding for the Affordable Care Act’s Medicaid expansion and the subsidies low- and middle-income families receive for private insurance, and do away with other key aspects of the law. But it wouldn’t attempt to replace them with anything. And it would cause chaos in the health insurance market by leaving in place Affordable Care Act regulations requiring insurers to cover everyone regardless of pre-existing conditions ― but without a mandate that people buy the insurance or help to make it more affordable.

The legislation would increase the number of uninsured by 32 million over 10 years, including 17 million next year alone, and the total would reach 59 million by 2026.

The other bill

And then there’s the House-passed American Health Care Act (which would leave 23 million more uninsured by 2026). Technically, the legislation must serve as the vehicle for whatever the “something” turns out to be because the Constitution requires bills with tax provisions to originate in the House. In these cases, the Senate typically strips these House bills of all their language and substitutes its own bill. Nevertheless, this measure still fits the definition of “something,” and the Senate could do whatever it wants.

What McConnell actually appears to be doing is teeing up a vote for all these bills, should he get 50 Republicans on the initial motion to proceed. In fact, he seems to be using the promise of a vote as the carrot to gain the support of reluctant senators. In essence, he’s saying, “Help me open debate, and you can vote for whichever bill you prefer!”

Somehow, this tactic seems to be working. Sen. Rand Paul (R-Ky.) opposes the Better Care Reconciliation Act, for instance, but may vote to start debate on the Obamacare Repeal Reconciliation Act, as may Sen. Mike Lee (R-Utah), who has been reluctant to back McConnell’s bill. And moderates, afraid of blocking their party from even debating repeal, may follow suit.

Uh-oh

But wait ― it gets more complicated.

McConnell revised the Better Care Reconciliation Act with new provisions added to win the support of Sen. Ted Cruz (R-Texas) that would create a two-tiered health insurance system in which insurers could sell two sets of policies. One would have to adhere to Affordable Care Act rules about pre-existing conditions and guaranteed benefits, while the other could exclude people based on their health status or medical histories.

Health insurers have warned that this won’t work, because healthy people would rush to buy the cheaper, skimpier plans, leaving sicker people behind in the other market, where their big medical bills would cause premiums to rise so much, they wouldn’t be able to afford insurance. And the healthy people would have policies so meager, they wouldn’t be adequately protected when the day comes that they stop being so healthy.

That Congressional Budget Office score of the Better Care Reconciliation Act doesn’t even factor in the effects of the Cruz amendment because the agency hasn’t had enough time to analyze it, so the Senate is set to begin debate on something no senators actually understand.

And if things go according to McConnell’s schedule and this all wraps up by week’s end, senators likely will be casting their final votes on something before the Congressional Budget Office can complete its work.

Uh-oh ...

And there’s even further complication.

The congressional GOP opted to use a special procedure called budget reconciliation to advance Affordable Care Act repeal because it can’t be filibustered in the Senate and thus can pass with just 51 votes ― including a possible tiebreaker by Vice President Mike Pence in his constitutional role as president of the Senate.

But this comes with a catch: Bills considered under budget reconciliation are supposed to be limited to matters directly affecting the budget, and provisions the parliamentarian deems don’t meet that standard traditionally must be removed.

On Friday, the parliamentarian announced that key parts of the Better Care Reconciliation Act weren’t kosher. They include funding cuts to Planned Parenthood and provisions limiting abortion, the absence of which would be a deal-breaker for conservatives, as well as insurance regulations seen as key to the new system the bill would create. And, like the Congressional Budget Office, the parliamentarian also hasn’t had time to review the Cruz amendment.

The world’s greatest deliberative body

This, to be absolutely clear, is highly abnormal. Congress gives more care and consideration to bills renaming post offices than it has to legislation with staggering consequences for the health care system.

So, to recap: Senate Republicans are moving forward with legislation that would gut Medicaid, vastly increase the number of Americans without health coverage, jumble the health insurance market in ways that could cause it to collapse, make it harder for people with pre-existing conditions to get and keep health coverage, and expose poor people to unlimited medical costs.

Only they don’t know what the legislation is or what, exactly, it would do. Now that’s really something.

Matt Fuller contributed reporting.