President Trump landed in McAllen, Texas, at the U.S.-Mexico border after leaving a message for open-borders Democrats: If you don’t help build a wall to stop the illegal-alien invasion of the United States, I’ll declare a national emergency and build it anyway.

Trump visited Ground Zero in the immigration debate just a day after abruptly walking out of a meeting with House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer when they again refused a compromise.

And so the government will remain shut down for the foreseeable future. Or at least until Trump does what he has threatened, and erect the barrier himself.

Talk in Texas

“Where you have a good strong barrier, you don’t have problems,” the president rightly said.

Trump met with border agents at a patrol station, Fox News reported, for a look at guns, drugs, and money they seized, including a rifle, handguns, a bag of cash, and “black-taped bricks of heroin and meth.”

Said Trump, “If we had a barrier of any kind, whether it’s steel or concrete they wouldn’t even bother trying. We could stop that cold.”

Trump also explained what he meant when he said Mexico would pay for the wall. “When I say Mexico’s going to pay for the wall.... I didn’t say they’re going to write me a check for $10 billion or 20 billion.” he said. “If Congress approves this trade bill, they’ll pay for the wall many times over. When I say Mexico’s going to pay for the wall, that’s what I mean.”

The New York Times reported this as an “untrue claim.”

But even before he boarded Air Force One, Trump reminded intransigent Democrats, who are trying to import illegal aliens to build a future voting base, that if they don’t do something soon, he’ll build the wall anyway.

“I have the absolute right to declare a national emergency,” Trump told reporters. “The lawyers have so advised me. I’m not prepared to do that yet, but if I have to, I will.”

So if the Democrats don’t come to their senses, “probably I will do it,” he continued, the Times reported. “I would almost say definitely.”

And he added a few thoughts about the back-and-forth with Pelosi and Schumer, the Washington Post reported. “I would like to do the deal through Congress,” he said. “It makes sense to do the deal through Congress.... It would be nice if we can make a deal, but dealing with these people is ridiculous.”

Many analysts thought — and many Americans hoped — Trump would declare an emergency in his talk to the nation Wednesday night. He didn’t, but he did show that the border is in crisis.

He presented a plethora of data, much of which was given to Congress in a briefing, to which Pelosi and Schumer didn’t even try to respond in their weak, ineffective attempt to smear the president.

Left Meeting

They continued that smear job after the president bolted what would have been a singularly unproductive meeting and waste of his time.

He met with Pelosi and Schumer in the White House yesterday. But then he asked whether they would provide the money for a border wall. Pelosi said no.

And that was that. “Just left a meeting with Chuck and Nancy, a total waste of time,” Trump tweeted. “I asked what is going to happen in 30 days if I quickly open things up, are you going to approve Border Security which includes a Wall or Steel Barrier? Nancy said, NO. I said bye-bye, nothing else works!”

Pelosi called Trump “petulant,” and Schumer again accused Trump of having a “temper tantrum,” and apparently, falsely accusing him of “slamming the table.” Vice President Pence said that didn’t happen.

Trump’s “temper tantrum” has been Schumer’s go-to fake-news narrative ever since Trump stood firm in the meeting with the two that preceded the government shutdown. “Cryin Chuck told his favorite lie,” Trump quipped.

Trump is to appear on Fox talker Sean Hannity’s program tonight, but as of now, it appears Trump just might have to declare an emergency to protect Americans from the continuing depredations of illegal aliens determined to break American immigration law by crossing the border, then telling mendacious tales of fear of violence and persecution for bogus asylum claims.

Should he do that, the radical Left will file multiple lawsuits that are likely already prepared, just as they were prepared when Trump rewrote the country’s rules on asylum claims to stop illegal aliens from using the procedure to stay in the country.

Photo: AP Images