The spectacle Donald Trump subjected the world to last week is unprecedented. The Republican nominee, having lost the first debate against Democratic nominee Hillary Clinton, went on a historic rampage.

He mostly attacked a person he could easily have ignored. Her name was Alicia Machado, a Venezuelan woman who won the Miss Universe pageant in 1996, the year Mr. Trump bought the company that operates the event.

She had complained about the sexist and degrading treatment to which Mr. Trump had subjected her, something Ms. Clinton threw at him unexpectedly during the debate.

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Instead of refocusing on his message after the debate, Mr. Trump lost his mind. The sting of a woman's criticism was something he couldn't ignore. He said hateful things about Ms. Machado in the press all week, and then overnight on Friday began tweeting the vile and demonstrably false accusation that Ms. Machado had appeared in a sex tape.

Mr. Trump also spent the week boasting that everyone agreed that he had won the debate, a claim that is self-evidently delusional. In spite of his claim to victory, he accused the moderator, Lester Holt, of bias; as proof, he claimed Mr. Holt had asked him a difficult question that was in fact raised by Ms. Clinton. He said Google was out to get him. And he gloated that newspapers that endorsed Ms. Clinton would lose readers.

In the middle of this madness, he showed flashes of the discipline that could get him elected, if he could stay focused. But his temperament is simply not up to the task.

What is there left to say about Donald Trump? His collapse in the first debate was followed by a predictable tantrum in which he has blamed everyone but himself for his poor performance. The shattering of his self-delusion about his invincibility exposed his unadulterated id. He was finally naked before the world, awake through the night in a pointless rage, tweeting out false accusations and grotesque insults at irrelevant opponents, and gloating about how they will suffer for their actions.

This is Donald Trump. This is who will be in the White House if he wins the election. No one can kid themselves any more.