Senate Republicans and President Trump may look back on Thursday as the day their relationship fundamentally changed. Both heretofore stalwart Trump defenders and skeptical moderates joined forces to embarrass the president.

To get the ball rolling, Senate Majority Leader Mitch McConnell (R-Ky.) gave up on the canard that he could not bring up anything for a vote that Trump wouldn’t sign. That was aimed at protecting McConnell from being undercut (again) but also at shielding Trump from an embarrassing display of disloyalty. He brought up the clean continuing resolution — something he vowed he would never do — and let a vote proceed. If he could do that Thursday, why couldn’t he have done it weeks ago? Well, of course he could have. He discovered that waiting for Trump to figure out how to get himself out of a jam was fruitless; he’d never get off his unsellable wall unless it went down in flames. It did. Since he has done it once, McConnell now can bring up all sorts of compromise proposals, in essence daring the president to veto them.

The counterpart to McConnell’s action was the defection of six GOP senators. Sens. Lamar Alexander (Tenn.), Susan Collins (Maine), Cory Gardner (Colo.), Johnny Isakson (Ga.), Lisa Murkowski (Alaska) and Mitt Romney (Utah) all voted for the continuing resolution. (Sen. Thom Tillis (N.C.), who is up in 2020, may regret not joining them.) The size and ideological diversity of the group were remarkable.

Thursday’s vote may, if we are lucky, mark the emergence of a core group of sensible Republicans who I have suggested could wield tremendous power. They can deny their party a simple majority, lure moderate Democrats into collective action and potentially push back against the worst aspects of this administration. With additional safety in numbers, they showed no hesitation in humiliating Trump on a vote that was never going to reach 60 needed for cloture anyway. By taking the vote, they put themselves in a position to find a way out of this debacle.

This could happen in other contexts. They could deny unqualified nominees, slow the buildup of debt, rebuff the president on Russia (11 Republicans voted to oppose lifting of sanctions on companies still controlled by Russian oligarch Oleg V. Deripaska) and forge a larger deal on dreamers, those on temporary protected status and even on legal immigration. (Interestingly, only Gardner and Collins were in both groups of GOP dissenters.) Once they discover that they can defy Trump with impunity, this may become a habit. After all, Alexander is retiring, Romney won’t be on the ballot for six years and Gardner is going to have to run as far from Trump as possible to avoid defeat in 2020.

We are still a long way from resolving the shutdown. If Senate Minority Leader Charles E. Schumer (D-N.Y.) is as shrewd as House Speaker Nancy Pelosi (D-Calif.), he’ll round up the six dissenters, reach out to other Republicans with tricky races in 2020 (e.g. Tillis, Martha McSally of Arizona) and find a dollar number for increased border security (but no wall). With even Trump loyalists such as Sen. Lindsey O. Graham (R-S.C.) trying to sway the president to open the government for a few weeks (just as Pelosi has been demanding!), there might be space for some grown-up negotiations.

The lesson here is that effective dealmaking is possible only when the Republicans abandon the world’s worst negotiator and refuse to cower before Fox News personalities.

Read more: