On Monday, President Biden shocked the political world by refusing to promise that the battle over the debt limit will be resolved without the United States defaulting on its debts, which would unleash economic calamity.

“No, I can’t,” Biden said, when asked whether he could guarantee resolution. “That’s up to Mitch McConnell.”

It’s anybody’s guess whether this effort by Democrats to ratchet up pressure on the Senate Minority Leader will actually work. McConnell (R-Ky.) is vowing to continue filibustering Democratic efforts to suspend the debt limit and avoid catastrophe.

But here’s one thing we can say right now: Biden’s declaration sets up the possibility for an endgame to all this that Republicans might not have anticipated. If this continues, it will soon become overwhelmingly clear that Republicans face a stark choice: Either they drop their filibuster, or we default.

McConnell has benefited overwhelmingly from the failure of media coverage to convey with real clarity precisely what Republicans are doing here. Oozing with bad faith, McConnell keeps insisting he just wants Democrats to raise the debt limit by themselves, offering this idea as though it’s the most reasonable notion in the world, packaged with his usual smarmy smirk.

It’s nonsense, of course. The idea that it’s solely Democrats’ responsibility to deal with the debt limit when they control Washington is an invented rule. Democrats and Republicans repeatedly suspended the debt limit under the last GOP president, when much current debt was racked up (and the debt limit is only about covering obligations already incurred).

More to the point, Republicans are filibustering Democratic efforts to suspend the debt limit. They’re actively blocking Democrats from doing what McConnell himself says he wants — that is, for Democrats to deal with this alone. He’s doing this to force Democrats to avert catastrophe in the reconciliation process, to disrupt their push for a multitrillion-dollar social policy bill.

Democrats are refusing to use reconciliation on the debt limit, and Biden’s new comments indicate that they appear determined to hold to this course. As Biden argued, if Republicans are not willing to help deal with the problem, they must at least drop their filibuster and let Democrats deal with it.

“They need to stop playing Russian roulette with the U.S. economy,” Biden said, which appears to mean he’s going to try to force them to relent.

It’s possible Democrats might back down, by, say, raising the debt limit themselves through reconciliation (another option that they should take seriously would be to try to use that process to nullify it entirely). But Democrats are running out of room to put that into effect by Oct. 18, which might be the deadline.

And so, if Democrats hold firm, we could soon find ourselves in a situation in which Democrats have no option of using reconciliation anymore.

If so, at that point, the choice for Republicans will be incredibly stark: Either they stop filibustering, or we default. All the game-playing will fall by the wayside. No matter how many times McConnell disingenuously pretends he only wants Democrats to handle this themselves while Republicans block this from happening, and no matter how many times McConnell is credulously portrayed as a savvy operator for doing so, as the days tick down to Armageddon, that will be his choice.

If Republicans continue regardless, Democrats may in turn have no choice but to carve out an exception to the filibuster to deal with the debt limit themselves. That might open the door for more carve-outs on the filibuster later.

Indeed, Sen. Richard J. Durbin (D-Ill.) just floated exactly this possibility:

So McConnell can smirk all he wants. He may not be smirking for much longer.