On Tuesday, fresh from a week of getting hammered over his belief that when neo-Nazis march into town and there's a terrorist attack you have to look for the nuance of "both sides," President Trump is going to Phoenix for what will surely be a lively rally. Whenever he feels beleaguered and put-upon, Trump heads for the warm embrace of his most ardent supporters, who reliably demand that he play all the old hits and know they won't be disappointed. "Lock her up! Lock her up!" they shout, like the crowd at a Billy Joel concert singing along to the words of "Piano Man."

Phoenix is a good place for this rally, since the state of Arizona has been on Trump's mind of late. One of the state's Republican senators, Jeff Flake, recently published a book critical of the president, which led the president to call Flake "toxic" and all but endorse one of his primary challengers. Trump is also considering a pardon for Joe Arpaio, the authoritarian goon who ruled over Maricopa County as sheriff for two decades. Arpaio was convicted of criminal contempt after a federal court ordered him to stop his relentless racial profiling and he went on TV to proudly proclaim he'd ignore the order, which makes him a natural for Trump's first pardon.

And when the president goes to Phoenix, he'll surely have to talk about that big, beautiful, 2,000-mile wall he was going to build along our southern border.

Remember that?

There was no single promise that was more important to Donald Trump's candidacy than the wall. It wasn't just about stopping undocumented immigration; instead, it was a symbolic vessel for everything Trump was about and would bring to his supporters. It would keep out the foreigners whom he said were stealing their jobs, killing their children, and transforming their communities. It would make America great again, like it was before all this multiculturalism that makes you feel alienated from your own home. It would hold back a threatening, unsettling, changing world.

And the masterstroke was his promise to make Mexico pay for it. The money didn't matter; the point was domination. He would make Mexico kneel before us, then dip into their own pockets to pay for their humiliation. Everyone would know who was standing tall and who had been defeated. The man who spoke endlessly about how other countries are getting the better of us and laughing at us would finally allow us to hold our heads up high and feel like victors again.

For people who felt like the world was beating them down, this idea was intoxicating. The only trouble was, the whole thing was a joke. Nobody who knows anything about the border thought that you could build a wall all the way across it — in many sections the terrain makes it extraordinarily difficult, and to do it you'd have to use eminent domain (which anti-government Republicans hate) to seize land from large numbers of Americans. And of course, Mexican President Enrique Peña Nieto made clear many times that Mexico would never, ever pay for the wall.

Then earlier this month, we got a window into how Trump sees the whole thing as a scam, when transcripts of a conversation he had early in his term with Peña Nieto were released. When Peña Nieto reiterated that they'd never pay for a wall, Trump responded, "But you cannot say that to the press. The press is going to go with that and I cannot live with that." He asked Peña Nieto to just say something vague when the question came up ("we should both say, 'we will work it out'"), but Peña Nieto refused, noting that "for Mexico, it is also an issue that goes beyond the economic situation because this is an issue related to the dignity of Mexico and goes to the national pride of my country." Exactly — robbing them of their dignity is the whole point, but the Mexicans are understandably not interested in playing their part in the show.

Not only that, Trump is having trouble getting his own Congress to agree to funding the wall. Because of disagreements within the GOP, Republicans may need Democratic votes to pass a budget bill, which has to take place before the end of September to avoid a government shutdown. But Democrats have made clear that they won't sign on to any bill that includes funding for a wall. Which makes it far more likely that Congress will pass a stopgap measure (known as a continuing resolution) to keep all funding at current levels while they put these kinds of tough decisions off for another day.

In the end, what will probably happen is that by the end of Trump's time in office there will be some beefed-up fencing in certain areas along the border, and some more border patrol agents, and lots more deportations. But what he promised from the moment he became a candidate — "I will build a great, great wall on our southern border. And I will have Mexico pay for that wall. Mark my words," he said in the speech announcing his presidential bid — that isn't going to happen.

So what is Trump going to say at that rally in Phoenix? Is he going to pretend that the wall is on track, and then do the old call-and-response that so thrilled his crowds during the campaign? When he says, "And who's going to pay for it?", will they shout back "Mexico!" with all the joy they did a year ago? Or has it begun to occur to them that maybe the whole thing was a lie, and they got suckered?