(On the GOP plan, only West Virginia’s Joe Manchin III broke with the Democrats, while immigration hard-liners Mike Lee of Utah and Tom Cotton of Arkansas voted against the proposal.)

(Philip Bump/The Washington Post)

The Republicans who voted against the GOP plan were Sens. Lamar Alexander (Tenn.), Susan Collins (Maine), Cory Gardner (Colo.), Johnny Isakson (Ga.), Lisa Murkowski (Alaska) and Mitt Romney (Utah).

While the measure failed, the Republican crossovers are significant. Shutdowns are about both sides holding the line — and that’s especially the case on the GOP side. Trump is demanding $5.7 billion in border wall funding or he won’t reopen the government, but six GOP senators just served notice that they won’t hold that line with him.

They’ll emphasize that they all voted for both bills, including the one with Trump’s wall funding, and that they just want to see the government open again. But their votes can’t help but present a somewhat divided and irresolute Republican front — in contrast to a very united Democratic one. They’re all saying they won’t make the same demand Trump is making. And when it comes to past shutdowns, this is generally how things begin to head toward a conclusion.

The vote, in the end, is the kind of vote that Senate Majority Leader Mitch McConnell (R-Ky.) could potentially use to persuade Trump to bring the whole thing to an end. And McConnell may not ultimately be that sad about it, given that he and Senate Republicans were prepared to pass a “clean” funding bill with no wall money before Trump decided to change course. That doesn’t mean it will be compelling to Trump, but it’s an argument that the shutdown strategy isn’t working.

And it’s only the latest. Republicans are clearly treading water on this issue. Polls already showed many more Americans blame Republicans and Trump for the shutdown than Democrats, and Trump was forced to back down from his State of the Union fight with House Speaker Nancy Pelosi (D-Calif.) on Wednesday. Now having six key defections has to have Democrats smelling blood.