Sen. Joe Manchin III’s declaration in a Post op-ed piece that there is “no circumstance in which I will vote to eliminate or weaken the filibuster” continues to stir angst. After all, if the West Virginia Democrat means what he says, filibuster reform won’t happen.

And let’s face it: His words sound awfully definitive. Yet some Democrats I’ve spoken with aren’t willing to give up on Old Joe quite yet.

Here’s why: Because in spelling out his case, Manchin has set up what one Capitol Hill Democrat described to me as “the Joe Manchin test.”

In his Post piece, Manchin makes the familiar argument that instead of nixing the filibuster, senators in both parties should just “put their heads down” and “tackle” our problems “together.”

In this telling, all that’s at issue is the personal comportment and civic virtue of individual senators, and those qualities live or die independent of the institution’s rules. But rules structure incentives, and the filibuster incentives the minority to withhold bipartisan cooperation, not the other way around.

We’ll soon see this illustrated in practice, by none other than the Joe Manchin test.

Buried in Manchin’s op-ed piece we find this:

Senate Democrats must avoid the temptation to abandon our Republican colleagues on important national issues. Republicans, however, have a responsibility to stop saying no, and participate in finding real compromise with Democrats.

Manchin places some onus on Republicans to cooperate with Democrats. And the Joe Manchin test will reveal that this isn’t going to happen — even though the filibuster, which is supposed to facilitate bipartisanship, remains in place.

This will soon become evident in several areas.

Infrastructure. Republicans love to claim President Biden’s new jobs plan contains tons of stuff that isn’t “real” infrastructure the way roads and bridges are. But Biden and Democrats are open to breaking up their proposal into numerous bills and trying to pass one narrowly focused on just that type of conventional infrastructure to win some bipartisan support.

That GOP talking point implies that Republicans should support a narrow bill focused on “real” infrastructure. But Republicans have ruled out tax hikes to pay for any of Biden’s plan. In theory, Republicans might support funding it with deficit spending, but they’re already committed to running in 2022 on the idea that deficits are exploding under Biden, so that’s also unlikely.

So where are 10 Republican votes (the amount needed to overcome a GOP filibuster) going to come from to support even a narrow infrastructure bill?

If and when they don’t materialize, that will be strike one on the Joe Manchin test.

“Dreamers.” Notably, Sens. Richard J. Durbin (D-Ill.) and Lindsey Graham (R-S.C.) formed a bipartisan working group to negotiate giving immigrants brought here illegally as children a path to legalization.

Yet Graham is already hinting that in exchange, Democrats must agree to changes that would block migrants from applying for asylum at the border and make it much harder for them to ever qualify for it.

That’s a nonstarter, because it would functionally gut our asylum system. It’s also a highly unreasonable demand, because numerous Republicans have already supported doing something to legalize dreamers. Graham long has, and so have numerous other GOP senators.

The fact that Senate Republicans are already talking about such a bitter poison pill suggests 10 GOP senators won’t support even this modest step to protect people who were brought here through no fault of their own and are thoroughly American.

That will be strike two on the Joe Manchin test.

Voting rights. Obviously Republicans will never support anything close to the sweeping federal voting rights protections that Democrats are seeking, since they require states to follow federal standards.

But theoretically, a few Republicans might support something more narrow, such as the John Lewis Voting Rights Act. That restores previously existing preclearance procedures for voting rules changes gutted by the Supreme Court, but in a more up-to-date way, while giving targeted states a way to show their practices should no longer require such preclearance.

Yet of course that won’t happen, given that Republicans are implementing voter suppression measures across the country. Which is exactly the point: 10 GOP senators will never support anything that moves toward leveling the electoral playing field, instead preferring to perpetually threaten Democratic aspirations to control Congress (which Manchin presumably wants) via anti-majoritarian tactics.

In his op-ed, Manchin implausibly suggests that voting reforms could have “bipartisan support.”

If and when his own prediction doesn’t materialize, it will be strike three on the Joe Manchin test.

It might be folly to expect voting rights — or the plight of the dreamers — to push Manchin into finally supporting filibuster reform. But as former senior Senate aide Adam Jentleson points out:

At some point, if Republicans keep failing the Joe Manchin test, he’ll have to admit that nothing will achieve the cooperation that can supposedly be achieved by senators simply rediscovering their inner civic virtue. And he’ll either have to revise his arguments, or reconsider his opposition to filibuster reform. You’d think, anyway.

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