Imagine, if you can, a scenario in which a special election in a deeply partisan state goes the other way unexpectedly, depriving a Senate majority in Washington of a vote it needs to pass a piece of contentious legislation.

The defeated but desperate majority party considers racing to enact the bill anyhow, in the stretch between election day and the day the new senator is seated, only to be thwarted internally by a heterodox, Vietnam War-veteran senator,who, in the spirit of regular order, says he will not participate in the legislative process until the election results have been certified.

If this strikes you as a long-shot means by which the Republicans’ indefensible and historically unpopular corporate tax cut bill might fail in the coming days—it is. But it is also a historically factual version of events by which Obamacare almost died.

On January 19, 2010, Republican Scott Brown unexpectedly defeated Democrat Martha Coakley in the Massachusetts Senate election. By then, the House and Senate had each passed different health care reform bills, but had yet to reconcile the differences between those bills in a conference committee. Brown’s victory deprived Democrats of their 60th vote. Final passage had abruptly become subject to a filibuster, and would thus fail—unless Senate Democrats took the aggressive step of rushing their work to completion before Brown could be seated, letting interim Sen. Paul Kirk (D-MA) cast a decisive vote on his way into the history books.

Senate Republicans unleashed a brief, preemptive uproar about this idea, but to their rescue came Sen. Jim Webb (D-VA).

“It is vital that we restore the respect of the American people in our system of government and in our leaders,” Webb wrote in an official statement. “To that end, I believe it would only be fair and prudent that we suspend further votes on health care legislation until Senator-elect Brown is seated.”

With that, many observers took Obamacare for dead. Eventually, House Democrats steeled themselves and passed the Senate bill unamended. Democrats figured out a way to tweak the bill with some minor budgetary changes, and the Affordable Care Act became law despite Brown’s victory. But it almost wasn’t so, and the disruption set in motion a cascade of events that left the health care law far more politically vulnerable than it otherwise might have been.

Now let’s get mad about some hypocrisy that hasn’t happened yet, but easily could.

After Webb hammered a nail into the ACA’s coffin, then-Senate Minority Leader Mitch McConnell praised him for thwarting Democratic “gamesmanship.”

“One concern I know a number of you had about the outcome of this election would be whether the new senator would be seated soon,” McConnell told reporters at a Capitol briefing on January 20, 2010. “I am convinced now that no gamesmanship will be played by the other side with regard to future votes in the Senate, thanks to Senator Jim Webb of Virginia. He’s made it clear that he will not participate in any additional health care votes prior to Senator Brown being sworn in…. Let’s honor the wishes of the people of Massachusetts and move forward.”

Shoe on the other foot, does anyone think McConnell would refrain from engaging in the very gamesmanship he decried eight years ago? The answer is almost certainly no—McConnell is a shameless hypocrite—but his hypocrisy would be immaterial so long as some Republican iconoclast made the same decision Webb did.

The Senate version of the Republican tax bill has already lost the support of Sen. Bob Corker (R-TN). GOP leaders secured the vote of Sen. Susan Collins (R-ME) on the basis of promises that they are in the process of breaking. If she walks away and Democrat Doug Jones defeats Republican/child predator Roy Moore in the Alabama Senate special election next week, then Republicans won’t have enough votes to clear a final tax bill and send it to President Donald Trump’s desk. Unless, of course, McConnell charges ahead, hoping to complete the process before interim Sen. Luther Strange (R-AL) gives way to new Sen. Doug Jones (D-AL).

Nobody should put this kind of procedural hypocrisy past McConnell. In this scenario it would all come down to whether less shameless senators—most particularly John McCain (R-AZ)—would consider it “regular order” to let a lame-duck senator cast the decisive vote on a widely loathed tax bill, after his party just lost his seat in an election.

I can’t claim to have an answer, but it is a hypothetical scenario we should take seriously. The balance Republicans have struck to keep their tax bill alive is extremely precarious. Their conference committee process has only just begun. And Moore is as close to victory today as Brown was several days out from his election in 2010.

There are obviously differences between the Alabama and Massachusetts special elections. Martha Coakley fell from political grace in a downward spiral around the question of whether she was a sufficiently dedicated Boston sports fan. Roy Moore’s downfall—if it is indeed a downfall—is the at least as troubling discovery that he is a pedophile. But the basic shape of politics is the same.

“I think you can’t just look at what happened in Massachusetts in isolation,” Sen. John Cornyn (R-TX) said eight years ago. “You have to look at what happened in Virginia, what happened in New Jersey.” Here in the present, Democrats just won landslide elections in Virginia and New Jersey, and Jones has not confined himself to running against Moore’s sexually predatory past, but against his regressive economic platform as well.

Should Jones win, and deprive Senate Republicans of their 50th and decisive tax bill vote, House Republicans could in theory still pass the Senate version unchanged. Unfortunately for them, their Senate counterparts cobbled together their bill so recklessly that they effectively wiped out all corporate tax expenditures, including ones Republicans love, by accident. The text they voted on included illegible scribbling, creating the further possibility that the House will unwittingly vote on legislative language that differs from the language in the bill that passed the Senate—which may in turn give rise to litigation. There would thus be a strong presumption, as there was after Scott Brown won, that the bill was dead. History hasn’t repeated itself yet, but it has a chance to do so uncannily.