In all my years, I have never seen anything quite like this: a U.S. president who lies and demonizes at the drop of a hat. I don’t just mean President Trump makes statements that tend to be inaccurate or misleading or that he exaggerates, equivocates and, at times, shades the truth.

No, this president repeatedly makes declarations that are flat-out at variance with established facts; assertions that on their face cannot be true.

As The Post’s “Fact Checker” column noted this week, until Wednesday, when Trump signed an executive order ending the separation of migrant families at the Mexican border, his “administration was insisting that it didn’t have a policy of separating families (false), that several laws and court rulings were forcing these separations (false), that Democrats were to blame (false), that only Congress could stop family separations (false) and that an executive order wouldn’t get the job done.”

No other words for it: Trump is a baldfaced liar.

Speaking to reporters on Air Force One, Trump said April 5 that he was unaware of a $130,000 payment to porn star Stormy Daniels ahead of the 2016 election.

From the White House transcript:

Q: Mr. President, did you know about the $130,000 payment to Stormy Daniels?

The President: No. No. What else?

Q: Then why did Michael Cohen make those if there was no truth to her allegations?

The President: Well, you’ll have to ask Michael Cohen. Michael is my attorney. And you’ll have to ask Michael Cohen.

Q: Do you know where he got the money to make that payment?

The President: No, I don’t know. No.

A few weeks later, Trump lawyer Rudolph W. Giuliani revealed that the president reimbursed Cohen, his personal attorney, for the $130,000 he paid to Daniels. After Giuliani spilled the beans, Trump reversed his position, disclosing in a sequence of tweets that Cohen had in fact received a monthly retainer “from which he entered into, through reimbursement, a . . . non-disclosure agreement” with Daniels.

Then there’s the Justice Department inspector general report on the investigation of Hillary Clinton’s emails. Said Trump: “I think that the report . . . totally exonerates me. There was no collusion, there was no obstruction.” The truth? The report said no such things. As Justice officials told the Senate Judiciary Committee, the inspector general did not delve into questions of collusion between the Trump campaign and Russia or whether he has obstructed justice in connection with special counsel Robert S. Mueller III’s investigation. The report was about Clinton, not Trump.

The list of lies goes way back: Trump’s “birther” lie, that President Barack Obama was a foreign-born Muslim; Trump’s charge that Obama had ordered wiretaps on the phones of Trump’s transition team; his assertion that he saw Muslims in New Jersey celebrating 9/11.

The Post keeps track of Trump’s falsehoods. As of May 31, the president had made 3,251 false or misleading claims since taking office. And there are no signs of him slowing down.

Trump’s penchant for lying, which stems back to his days of moving and shaking as a real estate mogul, is separate and apart from his reported sliming of brown- and black-skinned people to inflame, demonize and dehumanize: “Shithole countries” (Haiti, El Salvador, African nations); they “all have AIDS” (Haiti); won’t “go back to their huts” (Nigerians); they “infest our country” (immigrants).

“Why does he lie?” is a question many have tackled. I don’t know the answer. To accumulate and hold his grip on power? To bamboozle his supporters? To wiggle out of tight spots? The impact, nonetheless, is destructive. James P. Pfiffner, a public policy professor at George Mason University, wrote in a Brookings Institution blog that “Trump’s refusal to admit the truth of widely accepted facts corrodes political discourse and is consistent with the practice of many authoritarian leaders.” Trump’s narcissistic and demonstrably false statements about politics and policy, Pfiffner said, strike “at the very heart of democracy.”

No argument here. But there’s more: Trump’s lying is dragging the presidency through the mud. Through his incessant falsehoods, Trump has squandered the moral authority of his office. He cannot be believed. What did he and North Korean leader Kim Jong Un really say to each other in their one-on-one in Singapore? The president of the United States cannot be trusted.

Has America ever seen anything like this? Not in my lifetime. Donald Trump cannot go unanswered. He must be held accountable — by the law and at the polls. For America’s sake, nothing less will do.

Read more from Colbert King’s archive.