Following a declaration, the White House would still have to come up with funding for the wall without Congress’s help, which would require overriding appropriators’ spending decisions. That might well be unconstitutional and in any case risks infuriating appropriators, who jealously guard their power.

Read: Trump was always going to fold on the border wall

McConnell, as the head of the Senate and the top Republican on Capitol Hill, has been one of those warning against an emergency declaration, delivering his opinion in his typically understated, bland way. “I don’t think much of that idea,” McConnell told Charlie Homans of The New York Times Magazine in January. “I hope he doesn’t go down that path.”

He also reportedly warned Trump privately against the idea. McConnell told the president that if he declared an emergency, Congress might try to overrule him with a resolution, and that enough Republicans might join with Democrats that the resolution would succeed. Opinion among Republicans is not uniform; Senator Lindsey Graham of South Carolina has been a cheerleader for a declaration. But many Republicans have expressed misgivings, including on Thursday, and Trump’s decision to go forward sets up a test of their will to oppose the president.

Yet if McConnell himself is any indication, they are unlikely to push back. He flip-flopped on Thursday, announcing he’d support the president, despite his past public and private warnings against an emergency declaration. The GOP’s acquiescence wouldn’t be a surprise: While I have written that Trump almost always folds—and his decision to accept the compromise funding bill is yet another example—Republican members of Congress almost always fold, too.

With control of the one chamber, Democrats can force a battle over funding through spending bills, but only the GOP-controlled Senate can decide the fate of the emergency declaration by joining the House to vote against it. In one sign of their weak resolve, Republican members were reportedly demanding to know whether Trump would sign the funding bill before they held a vote—effectively delegating their decision to the White House.

That fits with the pattern. Despite having already passed a funding bill without money for the wall in December, they declined to force Trump’s hand and end the recent shutdown by voting for anything without his stamp of approval. Trump has stonewalled them on a report over the murder of the journalist Jamal Khashoggi, which the White House is legally required to provide, eliciting only some mildly affronted quotes from senators. They gave in to his decision to levy a range of tariffs on imports. Because of this pattern, it was especially surprising when the Senate voted to rebuke Trump’s plans to withdraw U.S. forces from Syria—in a nonbinding resolution.