The progressive push to force Justice Breyer into early retirement is still going on in the media but at least so far there’s no indication that Breyer is going to give in. In fact, the effort may have backfired by leading Breyer to determine he can’t leave under a cloud of partisan pressure.

While all of this has been happening, Democrats have been not-so-quietly worried about a specific worst case scenario in which the future of the court and the Biden agenda in Congress is brought to an abrupt halt by the death of a single Democratic Senator. If you think I’m kidding about that, I’m not. Both CNN and the NY Times raised that possibility last month. The Times piece was especially blunt, even naming the specific Senators that Democrats should be worried about:

Patrick Leahy, 81, Democrat of Vermont, was briefly hospitalized in January. Thom Tillis, 60, a North Carolina Republican, underwent cancer treatment. Questions have been raised about the health of Dianne Feinstein, 87, a Democrat who has represented California since 1992. Vermont’s other senator, Bernie Sanders, 79, had a heart attack in 2019.

You get the idea. Democrats are one heartbeat away from losing control of the Senate and that would put an end to Biden’s agenda and to any chance of confirming a progressive to replace Justice Breyer. That whole scenario was once again rehearsed in print by Salon on Wednesday:

Breyer waits to retire for a couple of more years, or even a few more months. Democrats lose control of the Senate in the 2022 midterm elections, or because an elderly member of their bare Senate majority passes away and gets replaced with a Republican, restoring Mitch McConnell to his perch as Senate majority leader. Breyer dies or becomes ill soon after Republicans retake the Senate and leaves the court. President Joe Biden, fulfilling his campaign pledge to nominate a Black woman to the Supreme Court, chooses a judicial superstar like California Supreme Court Justice Leondra Kruger or (soon-to-be D.C. Circuit Judge) Ketanji Brown Jackson. McConnell shamelessly announces that Republicans will hold no hearings for a Supreme Court justice until after the 2024 presidential elections, much like he ran out the clock on a hearing for Merrick Garland to fill the late Justice Antonin Scalia’s seat.

Again, what’s true for the replacement of Breyer is true for the Biden agenda as well. Both things are dependent on the Democrats’ narrow majority and are hanging by a thread. But if you think about it, Biden’s agenda is already on the ropes thanks largely to Senators Sinema and Manchin who are refusing to go along on some purely party-line votes. And that raises and interesting question. Given their willingness to buck their party on major legislation, can Democrats really assume they would vote for a progressive nominee for the court?

In a recent op-ed, Manchin, a West Virginia Democrat, doubled down on his opposition to eliminating the Senate filibuster. He also said he would not vote for the For the People Act—a sweeping voting rights bill that would override new voting restrictions passed by Republican state legislatures.

Newsweek reached out to Manchin’s office for comment on whether he would support a Biden Supreme Court nominee but didn’t receive a response before publication.

Bakari Sellers, a legal commentator who tweeted in January that Breyer should retire if Democrats won control of the Senate, said there’s “no question” Manchin could put the brakes on a Biden nominee.

“I have a great deal of concern of what he’ll look for in a justice,” Sellers told Newsweek.

Shooting down a Biden nominee for the court might be a bridge too far even for both Manchin and Sinema. However, their independent streak puts them in the role of kingmaker. Even if Justice Breyer gives in to pressure and retires tomorrow, Biden is going to have to select a nominee with an eye toward bringing Manchin and Sinema on board. And the nominee who will get their approval may not be the nominee that the progressives currently calling for Breyer’s retirement want. In short, it may already be too late for the progressive’s ideal replacement even if that process starts later this month.