Why in the world would President Trump, in the midst of the unrest roiling our nation’s capital, tweet a demonstrable lie about the city’s mayor, Muriel E. Bowser, and the D.C. police? Praising the U.S. Secret Service for their handling of protests at the White House, Trump tweeted that Bowser “wouldn’t let the D.C. Police get involved,” quoted an unnamed person as saying it’s “Not their job,” and ended the tweet with a sarcastic “Nice!”

Whether Trump’s unnamed person exists is unknown. What is clear, however, is that Trump’s accusation against Bowser and the police force was indisputably false. In fact, Trump’s lie was exposed the moment it left his mouth.

Led by D.C. police Chief Peter Newsham, and with Bowser’s knowledge and consent, the city’s police had already joined with the Secret Service and other federal law enforcement authorities to deal with White House and public demonstrations — as have D.C. mayors and police chiefs in the past.

In a news conference with Bowser, Newsham said he provided Secret Service officers with equipment they did not have, including riot helmets. “Wouldn’t let the D.C. Police get involved” Trump declared. The Secret Service issued a statement that said, “The Metropolitan Police Department and the U.S. Park Police were on the scene.”

Why would Trump tell such a baldfaced lie?

Perhaps, I should be the last person to ask that question, having devoted a recent column to his record of intentional dishonesty and deceit.

Yet to see, at this immediate and incendiary moment, the president intentionally telling a story as he wants it to be (or maybe believed), and not as it is — all without any regard for the consequences — is not only annoying; it should be alarming.

What world is he in? In the same four-part tweet, Trump said if the protesters had breached the White House fence, they would “have been greeted with the most vicious dogs, and most ominous weapons, I have ever seen.” Dogs and weapons have long been part of the Secret Service’s arsenal. Who is Trump trying to scare or buck up — himself, perhaps?

Trump fantasized: “That’s when people would have been really badly hurt, at least. Many Secret Service agents just waiting for action.” He again quoted an unnamed person: “We put the young ones on the front line, sir, they love it … good practice.”

In the book “Donald Trump and His Assault On Truth,” The Post’s Fact Checker staff observed that, when Trump inserts the word ‘sir’ in a story, “it’s often a sign that he’s telling a fairy tale.” The authors said their Fact Checker database has almost 100 claims involving a story in which some hapless soul calls Trump “sir,” which plays up his superiority.

In her Twitter rebuttal to Trump, Bowser depicts herself as standing with people peacefully exercising their First Amendment rights, characterizing Trump as hiding “behind his fence afraid/alone.” Bowser said, “There are no vicious dogs & ominous weapons. There is just a scared man.”

She’s right. Trump’s behavior isn’t just unpresidential. It’s bizarre. And we shouldn’t try to act otherwise.

What can you say about a person who persistently tells lies that are blatant and easily shown to be untrue? What about a president who — in the middle of angry protests and a pandemic burning across the nation — finds time to cast himself as a victim and pick a fight with a mayor who has done nothing to him? And doing it with a lie?

What’s the real story with Donald Trump?

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