Last week, President Trump was happy to fall on the sword for his border wall. Then on Wednesday, the White House seemed to indicate he would be willing to sign a short-term deal to keep the government open until early February.

But all of that fell apart Thursday morning when Trump began his day tweeting about the need for a border wall and placing the blame on GOP leadership for failing to get him the money he wants for it. A morning news conference by departing House Speaker Paul D. Ryan (R-Wis.) was hastily canceled after he spoke by phone with Trump, suggesting talks were breaking down.

The White House subsequently released a statement saying Trump “at this moment” is opposed to a deal without border security, “which includes steel slats or a wall.”

If Trump maintains a hard line stance on the wall and lets the government partially shut down Friday at midnight it won’t be because he couldn’t be swayed by incoming House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles E. Schumer (D-N. Y). It will be because he couldn’t be swayed by Republican leadership.

Trump has shown time and again that he cares way more about his supporters and his good standing with them than he does about the Republican Party. That has made him an impossible negotiating partner.

When it seemed as if Trump might cave, the right-wing media piled on. Ann Coulter called him “gutless,” and Breitbart News noted Trump’s walk-back of promises from the 2016 campaign (like the fact that “the big, beautiful wall” is now concrete slats). Moreover, Trump’s loyal foot soldiers on Capitol Hill are urging him to reject the spending deal, warning of the major damage it would cause Trump with his base and his 2020 reelection bid. In fact, the leaders of the Freedom Caucus are going to the White House on Thursday afternoon to deliver that message.

Adoration from his base is Trump’s lifeblood. The threat of losing his supporters' affection is enough to make him throw the rest of the GOP and the federal government under the bus. As soon as he started getting criticized by them, he yearned to appease them.

A similar dynamic played out over immigration earlier this year when Schumer offered Trump a deal: funding for his border wall in exchange for a path to citizenship for “dreamers,” the undocumented immigrants brought to America as children. Schumer believed Trump was on board, but as soon as Trump received pushback from his supporters, he turned down the deal.

Which, in a way, is how we got here. Trump never sticks with one line of thinking. His positions are constantly shifting, and he doesn’t provide any lawmakers on Capitol Hill any guidance of where his head is at any moment. The Senate passed a short-term funding bill Wednesday night believing he would sign it and woke up the next morning to find out he wouldn’t.

Then they have to start all over again. It’s needless brinkmanship of the kind Trump has played with Republicans for the past two years.

But things are about to get much worse for Trump next year. He knows, and his allies on the Hill know, that if they don’t push for the wall funding now, it’s never going to happen.

Because in January, Trump won’t have the luxury of a GOP leadership in the House to bend the knee. Pelosi will control the agenda, and Trump will be forced into the untenable position of actually negotiating and risk losing support from his base, or sticking to his hard-line views and getting absolutely nothing for it.