President Trump. (John Minchillo/AP)
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When it’s all over, the most enduring damage may be not to civility, the rule of law or even America’s standing in the world.

The wound that may longest outlive President Trump and his enablers will be the racial and ethnic fear and hatred they so cynically stoked and exploited.

Why is it, after all, that on the day last week that his former lawyer and campaign chairman found themselves judged in federal court, the president declared at a West Virginia rally that “the beating heart of this election is border security”?

Even Trump cannot believe that the greatest problem facing America today is Mexicans or Hondurans sneaking across the border. No, but what began for him as little more than a joke has turned into a matter of survival-by-distraction.

“You know,” he said fairly early in his campaign, “if it gets a little boring, if I see people starting to sort of, maybe thinking about leaving, I can sort of tell the audience, I just say, ‘We will build the wall!’ and they go nuts.”

That was January 2016. By a year later, he was “in a little bit of a political bind,” as he told Mexico’s president, Enrique Peña Nieto on Jan. 27, 2017.

“I have to have Mexico pay for the wall — I have to,” Trump said during a telephone call, a transcript of which was leaked months later. “I have been talking about it for a two-year period.”

He explained the politics during an interview with the Associated Press in April 2017: “My base definitely wants the border wall, my base really wants it — you’ve been to many of the rallies. Okay, the thing they want more than anything is the wall.”

Last week he was not just following his base — he was doing all he could to inflame it.

“A vote for any Democrat in November is a vote to eliminate immigration enforcement, throw open our borders, and set loose vicious predators and violent criminals,” he said during a West Virginia rally. “They’ll be all over our communities. They will be preying on our communities.”

These are falsehoods predicated on falsehoods. No Democrat supports open borders. And, though Trump and Fox News fearmonger Tucker Carlson will always be able to find inflammatory cases of young white women killed by sinister brown men, studies overwhelmingly show that immigrants, including illegal immigrants, commit crime at far lower rates than do native-born citizens. As the percentage of foreign-born increased in the United States from 7 percent to 13 percent between 1990 and 2013, violent crime rates fell 48 percent.

Politically, though, what matters is the first statistic — the increase in foreign-born. During the George W. Bush presidency, Republicans saw this as an opportunity. The voting population was going to become more diverse; Hispanics and Asians were potential Republican voters; the GOP should reach out. It may have been self-serving; it also was good for the country.

Trump Republicans see an opportunity of another kind. Not surprisingly, the increasing diversity has proven unsettling to some Americans, particularly in areas unaccustomed to immigration. By appealing to their fears, Trump hopes to win their votes.

“Immigration as an issue is a winner for Republicans when we make it about security and crime,” Republican pollster Chris Wilson recently told Post reporters David Nakamura and Sean Sullivan.

But on this issue, you can’t leach away the moral implications.

His dependence on this issue guarantees that Trump will not accept the legislative solutions to actually begin to solve the immigration problem. That means that “dreamers” remain in limbo, farmers are short of workers, America is losing ground in science and families are being needlessly torn apart.

It means he has put America on the side of rising white nationalism and incipient fascism in Europe and elsewhere. Last week, Trump finally found a human rights cause he could embrace: on behalf of white farmers in formerly apartheid South Africa.

It means he is not working with Mexico and Central America on the one thing that would solve the border problem once and for all, which is enough prosperity south of the border so that people could stay at home, which is generally what people want to do.

And it means that the always fraught challenge of incorporating this generation of immigrants — assimilating, learning from, being enriched by — will be that much harder and take that much longer. It will happen; most of those people are not going away, no matter how much Trump dreams of deportation, and the country’s adaptive genius will be stronger than the Trump poison.

But the poison will linger. And when history considers how the Mitch McConnells and Paul Ryans acquiesced to Trump’s many depredations, it will be their failure to stand up for respect and tolerance between one human being and another that will be judged most harshly.

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