“He was wacky,” Mr. Trump said. “Boy, did he fold up like a wet rag, huh? Man. Man. He was gone so fast, O.K.?”

“Oh, he did something,” he said, adding, “‘Oh, oh, oh, I resign, I quit.’”

“I don’t want to mention Al Franken’s name, so I won’t mention.”

The remark was in keeping with Mr. Trump’s long-stated personal mantra of never giving in to any accusation, and considering those who do to be weak. But it came at a fraught moment when four senators, two of them Republican women, remain undecided about whether to vote to confirm Judge Brett M. Kavanaugh to the Supreme Court. A crucial procedural vote is scheduled for Friday morning.