Donald Trump’s long-tortured relationship with the truth is nearing a point of total estrangement.

The Republican presidential nominee tweeted over the weekend that rival Hillary Clinton and her fellow Democrats “are trying to rig the debates” by scheduling them during NFL games. (In fact, the bipartisan debate commission, independent of parties and candidates, announced the dates on Sept. 23, 2015.)

He further alleged that “I got a letter from the NFL saying, ‘This is ridiculous.'” (The National Football League says it sent no such letter.)

In an epic interview with ABC News’ George Stephanopoulos, Trump declared that Russia’s Vladimir Putin “is not going to go into Ukraine.” (Russia has been in Ukraine since 2014.)

Trump further asserted that “I have no relationship with Putin,” “I never met him” and “I have never spoken to him on the phone.” (In 2013, he said that “I do have a relationship” with Putin, and in 2014 he said, “I spoke indirectly and directly with President Putin, who could not have been nicer.”)

Trump alleged that “Hillary’s script writers” wrote the Democratic convention speech given by the father of a Muslim American soldier who was killed in Iraq (the father, Khizr Khan, spoke without notes) and suggested that the soldier’s mother “wasn’t allowed” to talk because she’s Muslim (she says she was too upset).

Asked to respond to Khan’s charge that Trump has “sacrificed nothing,” Trump cited his work on New York’s Vietnam memorial in the 1980s.

(A contemporaneous report in The Washington Post said Trump attended only two or three of the 20 memorial commission meetings, accompanied to one by a reporter profiling him.)

It was a bravura performance – but hardly unique. If you want to know whether something Trump says is true, flip a coin. Even this method overstates his honesty.

Certainly, Clinton tells whoppers, too. But Glenn Kessler, The Post’s Fact Checker, tells me that in his six years on the beat, “there’s no comparison” between Trump and other politicians. Kessler says politicians’ statements get his worst rating – four Pinocchios – 15 percent to 20 percent of the time. Clinton is about 15 percent. Trump is 63 percent to 65 percent.

PolitiFact, similarly, rated Clinton statements false 28 percent of the time (including 2 percent rating “pants on fire,” the worst rating), while rating 70 percent of Trump statements false (including 17 percent “pants on fire”).

Journalists hesitate to call these falsehoods “lies” because it’s hard to know whether ignorance or malice is to blame. But in Trump’s case, there’s a third possibility that is particularly alarming: He may not be able to tell fact from fiction.

“Lying is second nature to him,” Tony Schwartz, Trump’s ghostwriter for “The Art of the Deal,” told the New Yorker’s Jane Mayer in an article published last month. “More than anyone else I have ever met, Trump has the ability to convince himself that whatever he is saying at any given moment is true, or sort of true, or at least ought to be true.”

He manufacturers falsehoods by the hundreds: that Muslims celebrated in New Jersey when the Twin Towers collapsed, that a U.S. general executed Muslim prisoners with bullets dipped in pig blood, that immigration is at a record high, that U.S. taxes are the highest in the world and that the unemployment rate could be 42 percent.

There isn’t space to mention most of Trump’s whoppers, so let’s take a simple category: those in which Trump debunks himself.

He claimed that he never promised to raise $6 million for veterans, that he wanted to keep his fundraising for veterans quiet, that he never offered to pay legal fees for supporters who hit protesters, that he doesn’t “know anything about David Duke,” that he “never mocked” a disabled reporter, that he opposed the Iraq invasion “loud and strong” from the start and that he didn’t support the attack on Libya.

In each case, video, audio and written evidence proves otherwise.

So, too, do the facts refute his denials that he called John McCain a “loser,” objected to Fox News host Megyn Kelly as a debate moderator and used a vulgar word to describe Ted Cruz at a campaign rally.

In each case, Trump surely could have known that a simple internet search would prove him a liar. This suggests that he may not think he’s lying – and that he sees truth not as an absolute but as the last thing to come out of his mouth.

Dana Milbank is a columnist for The Washington Post. He can be contacted at:

danamilbank@washpost.com