President Donald Trump’s obsession with a border wall with Mexico has now kept the government partially shut for three weeks. But the commander in chief didn’t always think it was such an essential idea. In fact, it started out as a gimmick, or, as the New York Times calls it, “a mnemonic device of sorts.” During the time when Trump was weighing his presidential candidacy, aides wanted to come up with a way to help him remember to talk about getting tough on immigration, which was always seen as a key issue in his campaign.

Political advisers Sam Nunberg and Roger Stone apparently came up with the idea. “How do we get him to continue to talk about immigration?” Nunberg claims he told Stone. “We’re going to get him to talk about he’s going to build a wall.” The plan worked like a charm. Trump talked about immigration in his speeches, and the wall narrative got huge reactions from the crowd, which obviously thrilled Trump. So he kept pushing the idea harder and harder.

The laser focus on the wall, though, makes even some immigration hardliners nervous, because most don’t actually see it as the most important priority. And some who agree with Trump that immigration needs to be curbed worry that he’ll be willing to trade away things that are far more important in order to get his wall. “I’ve always thought it created a danger that he would trade almost anything in order to get the wall,” said Mark Krikorian, the executive director of the Center for Immigration Studies. “I’m still worried about that now.”

Michael D’Antonio, a Trump biographer, says the wall is naturally appealing to Trump because of his background in real estate and the idea that he’d leave behind a legacy. “I think he’d like it being called the Great Wall of Trump,” D’Antonio said, noting he’d probably like it even more if there was a plaque honoring the president who built it “every mile or so.”

For now, it seems the wall remains an impasse, and negotiations to reopen the government aren’t really getting anywhere. “We didn’t make much progress at the meeting, which was surprising to me,” acting White House chief of staff Mick Mulvaney said Saturday. In a meeting that included Vice President Mike Pence, the administration continued pushing for cash to build the wall. Negotiations are set to continue Sunday. Trump wrote on Twitter that “not much headway made today” before continuing with his message: “After so many decades, must finally and permanently fix the problems on the Southern Border!”

V.P. Mike Pence and team just left the White House. Briefed me on their meeting with the Schumer/Pelosi representatives. Not much headway made today. Second meeting set for tomorrow. After so many decades, must finally and permanently fix the problems on the Southern Border! — Donald J. Trump (@realDonaldTrump) January 5, 2019