In short, he's using lies to try to claim his original lie wasn't actually a lie.
Also yesterday, the Canadian newspaper The Globe and Mail published an editorial (link here) titled: "Donald Trump Lies Constantly. Why Is It working for Him?" That piece explores how Trump's torrential lying is unprecedented in a President.
The op-ed refers to "the relentless stream of lies and false provocations flowing from the mouth and Twitter feed of the current President, Donald Trump."
Doubtless most of us have know an outrageous liar or two or three in our personal lives. They tell such elaborate and unbelievable tales we know not to believe anything and everything that comes out of their mouths unless we hear independent corroboration, which rarely happens.
Usually such lies are harmless, the hallmarks of a benign braggart. They tell tales about places they've been where we know they've never visited, their experiences we know they've never had, their encounters with famous people we know they've never met.
Sometimes, unbelievably, astoundingly, someone else we know is naive enough to believe these impossible fibs. That's what the liar lives for, a dupe who will believe his fantastical tales.
Such behavior amongst acquaintances is rarely of consequence. But when the President of the United States is constantly telling tall tales, and his naif supporters consistently believe him, then we could end up in dire circumstances.
The great danger is this: a fabulist head of state often metamorphosizes into a tyrant. Look at any famous dictator in history and you'll see a man who started out spinning tangle after tangle of lies, then kept lying until it was too late to stop him.
We must not let that happen here.