All this became blindingly obvious Tuesday, which by any reasonable standard should have been doomsday for his White House aspirations. A news conference about his fundraising for veterans causes was the site of the scariest meltdown since the Fukushima nuclear disaster.
That coincided with the release of evidence from a lawsuit against Trump University indicating it was, as one sales manager attested, "a fraudulent scheme" that preyed ruthlessly on the vulnerable and the gullible.
What did we learn about the man who may become president? Nothing that came as a complete surprise but plenty to prove he is even worse than previously realized: a pathological narcissist, a world-class whiner, an indefatigable con artist and a vicious enemy of anyone seeking the truth.
Trump's eruption against the news media was that of someone who is so hopelessly in love with himself that he thinks he can do no wrong. Anyone who doesn't automatically agree, in his view, is not just mistaken but corrupt. He said, "I find the press to be extremely dishonest. I find the political press to be unbelievably dishonest."
What provoked such venom? The objects of his ire were doing one of the most basic tasks of journalism: taking note of claims and promises he made in his campaign and trying to find out whether he has done what he said.
But it turned out the amount was several hundred thousand dollars short of his claim. He didn't give the $1 million of his own money he had promised until last week, after reporters inquired about it. Many of the other checks sent to veterans organizations were not cut until May 24 -- nearly four months after his event. At least one gift went to a group that spends only 10 percent of its funds on programs for veterans.
Rather than manfully address his own lapses and delays, Trump threw a pity party for himself. "Instead of being like 'Thank you very much, Mr. Trump' or 'Trump did a good job,' everyone's saying, 'Who got it, who got it, who got it?'" he bleated. "And you make me look very bad. I have never received such bad publicity for doing such a good job."
The searing injustice he decried brings to mind what Oscar Wilde said about a particularly heart-rending scene in a Charles Dickens novel: "One must have a heart of stone to read the death of little Nell without laughing."
Following through on commitments is part of being an adult. Accounting for your conduct is something you should mind only if you have something to hide.
Trump has a lot to hide. The lawsuit against Trump University has uncovered information to suggest that the chief education its students received was in the folly of trusting him.
One former sales executive said Trump's promise to be "actively involved" in the classes "was not true" and his school was "a total lie." Another employee quit over "fraudulent and dishonest" tactics he was expected to use in fleecing potential customers.
The judge who ordered the release of this material got the same treatment as anyone who doesn't take Trump's word as gold. Trump said U.S. District Judge Gonzalo Curiel is "Mexican" and a "hater of Donald Trump." Curiel, born in East Chicago, Indiana, served 17 years as a federal prosecutor. Like the news media, he is vilified by Trump for simply carrying out his duties.
The picture of Trump on view this week is an unstable egomaniac and dishonest huckster who sees enemies everywhere. His supporters may enjoy seeing him snarling and snapping like a rabid dog.
What makes them so sure that, someday, he won't bite them?