By Gary Abernathy Special to the Washington Post

If President Donald Trump agrees to end the partial government shutdown without a deal to fund a southern border wall, it’s an exaggeration to say his supporters would abandon him. But they would be disappointed and, in some cases, angry – and the enthusiasm of his base is much more important than their actual numbers as reflected in any given poll.

Trump’s tough stance on curtailing illegal immigration was a cornerstone of his candidacy and a big reason for his election victory. Even if he pursues a strategy of building a wall by declaring a national emergency, his supporters know that the courts could shoot that down with the stroke of a pen. They understand that the only way to ensure the wall gets built is with congressional sign-off, and the only way that happens is for House Speaker Nancy Pelosi, D-Calif., and Senate Minority Leader Chuck Schumer, D-N.Y., to cry uncle on the shutdown standoff before Trump does.

When it appeared a few weeks ago that Trump was ready to capitulate and agree to a short-term budget resolution without wall funding, his supporters in my neck of the woods and elsewhere were shaking their heads. They want the president to play hardball, and word obviously reached the White House that such a deal would be seen as surrendering to Pelosi before she even took up the gavel.

One talking point by Democrats and many in the media that Trump had promised the wall would be paid for by Mexico is almost irrelevant to the president’s base. Trump is claiming lately that his new trade deal means Mexico is paying for the wall “indirectly,” but that thin defense is aimed only at his critics who pretend to care. His core supporters never did.

It’s been accurately pointed out that Trump’s critics take him literally but not seriously, while his supporters take him seriously but not literally. Trump’s campaign consisted of giant pep rallies, televised so often that future attendees knew what to expect and how to participate. From chants of “lock her up” to repeating the various nicknames with which Trump labeled his opponents, everyone had the script and knew when it was their turn to read their lines, like the litanies of a church.

“Who’s going to pay for the wall?” Trump would ask.

“Mexico!” the crowd would roar in response, most people laughing even as they played the game. It was made even more fun when former Mexican president Vicente Fox grew so outraged that he used an expletive to fire back with the promise that “We’ll never pay for that f——— wall!” Well, of course not, but thanks for playing.

But Trump’s base takes the wall itself seriously, and, like George H.W. Bush’s 1988 campaign pledge on taxes, the wall has become the president’s “read my lips” albatross. His supporters may not abandon him over it, but Trump’s re-election hinges entirely on their enthusiasm. Yes, they will vote for him, but will they engage in the get-out-the-vote activities that drive to the polls enough additional voters to put Trump over the top?

In rural America, where property lines are regularly defined by fences and gates to keep livestock in, families and property secure, and trespassers out (“No Trespassing” signs are as common here as stoplights in the city), defining and defending our southern border with a wall is just common sense.

But whether it’s built or not, the wall – or barrier, or fence – has become entirely symbolic, something the Democrats know as well, especially those who just a few years ago supported the need for such barriers and voted for much more money for border security than the $5.7 billion the president now requests.

So successfully have critics blurred the distinction between legal and illegal migrants that the president is often accused of being “anti-immigration,” and the wall has come to symbolize the United States’ core philosophy about immigration itself.

“There are no such things as illegal people,” Trump’s critics say. True, but there are still such things as people coming into the United States illegally, at least for now. The degree to which borders actually matter – and how our national security is defined – will be largely determined by which side wins the battle over the wall.

If Pelosi, Schumer and company prevail, it will make Trump a loser on his top priority. Weak-kneed Republicans in Congress will start to peel away. Trump’s base didn’t take him seriously on Mexico paying for the wall, but they took him literally on the wall being built. On this, he has no choice but to stand his ground.

Gary Abernathy, a contributing columnist for the Post, is a freelance writer based in Hillsboro, Ohio.