There’s a reason he’s so fixated on Wall – the fact that he’s a racist shithead, yes, but an additional reason. Eric Lach at the New Yorker:

So why did he do [the emergency]? When a reporter pressed him on whether he would concede that he didn’t get the deal he wanted from Congress, Trump, of course, refused to concede. And, in doing so, he undercut what little concrete rationale his emergency had to begin with. “I could do the wall over a longer period of time. I didn’t need to do this. But I’d rather do it much faster,” he said. “And I don’t have to do it for the election. I’ve already done a lot of wall for the election. 2020. And the only reason we’re up here talking about this is because of the election—because they want to try to win an election, which it looks like they’re not going to be able to do.” So there it is, as straight as you can get it from this President: he didn’t need to do this, and it’s not about the election, but the only reason he’s talking about it is because of the election.

It’s a good day to remember that, according to Joshua Green’s “Devil’s Bargain,” Trump’s aides came up with the idea of the wall in 2014, not for policy reasons but for memory reasons. “Inside Trump’s circle, the power of illegal immigration to manipulate popular sentiment was readily apparent, and his advisers brainstormed methods for keeping their attention-addled boss on message,” Green wrote. “They needed a trick, a mnemonic device. In the summer of 2014, they found one that clicked.” Not with the public, or even with the Republican Party—but with Trump himself.

Wall. He can remember it. It’s just four letters, it’s a familiar word, we’ve all seen walls, some of us have them in our houses or apartments or cells. Wall. You don’t even need an article, you can just call it Wall as you might call it Don or Dan or Dun. Wall.