The Senate on Tuesday afternoon will cast its first procedural vote related to health care reform. That is about as specific as I can get to describe the ridiculousness of what they’re attempting to do today. There have been no public hearings, no final Congressional Budget Office score, no final guidance from the Senate parliamentarian, and no efforts to sell this to the public. And what is “this”? I don’t know, senators don’t know, no one knows.

“The Senate health care bill” does not really exist. Senators are being asked to vote for a motion to proceed into the unknown, with the promise that something will be figured out in the next couple of days of open debate after a couple of show amendment votes fail. The latest speculation is that McConnell’s ultimate fallback plan would be a vote on a “skinny” repeal that just eliminates a couple of Obamacare’s taxes and then punts the repeal process into a conference committee with the House. A stunning number of Republicans are willing to go along with this. In the spirit of the past two years of American politics, this is a national embarrassment, and it could work.

Since he does not have 50 votes to pass any particular health care bill, Senate Majority Leader Mitch McConnell is trying to open debate under a fog of confusion, and the only clear statement he’s willing to offer his members is the repercussion: If you vote against advancing to debate on the mystery bill, you love Obamacare.

Since last week, McConnell has been trying to woo different segments of his caucus to vote “yes” on the motion to proceed by offering them votes on the specific bills they want (or can best tolerate). He is trying to get Kentucky Sen. Rand Paul, Utah Sen. Mike Lee, Kansas Sen. Jerry Moran, and potentially others to support the motion to proceed by dangling an amendment vote on the 2015 “repeal-only” bill. He is trying to get moderates, and those most concerned with the repeal-and-replace bill’s Medicaid cuts, onboard by offering to plow some $100 billion earmarked for Medicaid recipients into the still-mysterious repeal-and-replace plan. (That $100 billion, on top of the rest of the Better Care Reconciliation Act’s spending on low-income people, will still come nowhere near the $750 billion that BCRA cuts from Medicaid in the first 10 years.)

McConnell can afford to lose two Republican votes on the motion to proceed. He can thank Arizona Sen. John McCain for the luxury of that second lifeboat, since McCain, who was diagnosed with brain cancer last week, announced Monday night that he would be returning to Washington.

Maine Sen. Susan Collins is the hardest “no” on the procedural vote, telling reporters Monday that since she would not vote for any version of any bill that’s been floated so far, she will not vote to proceed.

With Collins out, McConnell can afford to lose just one more of the following undecideds: Paul, Lee, Moran, Alaska Sen. Lisa Murkowski, Nevada Sen. Dean Heller, Ohio Sen. Rob Portman, West Virginia Sen. Shelley Moore Capito. None of these senators are jazzed about submitting themselves to a vote-o-rama—the rapid fire process of amendment offerings, debate, and votes, which the motion to proceed would kick off—with no solid game plan except the certainty that two health care bills would be voted on, at least one of which each of these members strongly dislikes and neither of which have a chance of passing.

And yet it could happen, because a classic, deadly case of Washington logic is asserting itself. It quickly became the consensus belief Monday night that McCain’s return provides the “momentum” needed to advance “this.” How cruel, the thinking goes, would it be to drag McCain out here for a failed vote? Well, it would be far less cruel than voting to advance a debate on multiple bills you otherwise believe to be white-hot, radioactive garbage. Voting for something bad because you were impressed with a colleague’s logistical arrangements would be Peak Senate. Watch out.

The vote will occur sometime in the midafternoon.