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Donald Trump will never give up on The Wall.

On Wednesday, Chief of Staff John Kelly sat down with Fox News’s Bret Baier and made the case that he was the adult in the room. The gist was that the president may be uninformed and immature, but Kelly was informed and mature. To illustrate this fact, Kelly used his conversations with Congress about Trump’s central campaign promise: The Wall.

As we talked about things—where this president is and how much he wants to deal with this DACA issue and take it away—I told them that, you know, there’s been an evolutionary process that this president has gone through as a campaign. And I pointed out to all of the members that were in the room that they all say things during the course of campaigns that may or may not be fully informed. But this president, if you’ve seen what he’s done, he has changed the way that he’s looked at a number of things. ... So he has evolved in the way he’s looked at things. Campaign to governing are two different things, and this president is very, very flexible in terms of what is within the realm of the possible.

Trump responded by implicitly blasting his chief of staff for suggesting that he has “evolved” on the issue.

The Wall was a quintessential campaign promise in that it was largely symbolic. Insisting that the United States (or, sometimes, Mexico) build a costly and expensive border wall was a supposed “common sense” proposal—never mind that it’s ineffective—meant to illustrate the difference between Trump and the bureaucrats dictating immigration policy. But Trump has never grasped the subtlety of his own messaging and has continued to insist on a literal wall.

The irony of these tweets is that it’s clear that Trump still isn’t “fully informed” about his signature promise or who will pay for it. There has been an expectation that, at some point, the president would have to recognize its infeasibility. But it looks like that won’t happen anytime soon.