Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Minority Leader Nancy Pelosi (D-Calif.) thought they had a deal with President Trump. Knowing how unreliable he is, they quickly shot out an announcement Wednesday night after their dinner at the White House:

We had a very productive meeting at the White House with the President. The discussion focused on DACA. We agreed to enshrine the protections of DACA into law quickly, and to work out a package of border security, excluding the wall, that’s acceptable to both sides.
We also urged the President to make permanent the cost-sharing reduction payments, and those discussions will continue.

Predictably, Trump’s base freaked out. The president had been snookered, giving the dreamers “amnesty” and not getting his wall. By morning, Trump was in full retreat, tweeting: “No deal was made last night on DACA. Massive border security would have to be agreed to in exchange for consent. Would be subject to vote. … The WALL, which is already under construction in the form of new renovation of old and existing fences and walls, will continue to be built.” But then again, he demonstrated he has no stomach for deporting the dreamers: “Does anybody really want to throw out good, educated and accomplished young people who have jobs, some serving in the military? Really!” Well, actually he did and his base still does.

President Trump said on Sept. 14 that he's working with Democrats on a plan for DACA "subject to getting massive border control." (Reuters)

Schumer and Pelosi were not about to let a deal this good slip away. They put out yet another statement:

President Trump’s tweets are not inconsistent with the agreement reached last night. As we said last night, there was no final deal, but there was agreement on the following:
We agreed that the President would support enshrining DACA protections into law, and encourage the House and Senate to act.
What remains to be negotiated are the details of border security, with a mutual goal of finalizing all details as soon as possible. While both sides agreed that the wall would not be any part of this agreement, the President made clear he intends to pursue it at a later time, and we made clear we would continue to oppose it.
Both sides agreed that the White House and the Democratic leaders would work out a border security package. Possible proposals were discussed including new technology, drones, air support, sensor equipment, rebuilding roads along the border and the bipartisan McCaul-Thompson bill.

Schumer and Pelosi achieved one of two things, maybe both. They may have secured a deal for dreamers without anything that Democrats find all that objectionable. Trump is so anxious for a deal that he’ll no doubt sign anything put in front of him that spares him the task of following through on the assurances that his anti-immigrant supporters thought they had. And Schumer and Pelosi have shown Trump’s base for the second time within the span of a week how thoroughly unreliable Trump is.

President Trump's position on DACA has taken several twists and turns over the years. (Meg Kelly, Claritza Jimenez/The Washington Post)

Trump has demonstrated over and over that he cares nothing about the substance of any deal. He wants praise from whoever is in front of him at the moment and praise from the media, which despite his bashing, he desperately needs to tout his wonderfulness. Unfortunately, that does not work in politics. where the substance matters tremendously to politicians and their supporters. Trump has never been a “Republican” and indeed has never been shy about turning on a dime (e.g. on abortion) if he thought it would benefit him. As a result of his frantic, utterly unprincipled search for a deal, he has essentially convinced both sides that they cannot take him at his word.

That, ironically, makes dealmaking on controversial issues impossible. Do Democrats believe him when he says he wants no tax cuts for the rich? Or do Republicans believe his emissaries, who bring proposals that most certainly benefit the rich — a lot? Republicans who pass a typical supply-side bill risk getting smacked by the president (as they were when he declared their health-care plan “mean”). Under such circumstances, it’s hard to imagine Republicans unifying around a specific plan with the assurance that the president will stand behind it.

All of this goes back to the fatal error and morally bereft calculation that House Speaker Paul Ryan (R-Wis.) and other Republicans made. Sure, Trump is a narcissist, a know-nothing, a racist — but he’ll sign our bills! Actually, he won’t. Character always matters, and in this case, Republicans are paying the price for their Faustian bargain.