“It’s something else — it’s feeling, emotion, preference, loyalty, convenience of the moment,” Mr. Hayden said. He quoted a former speechwriter for Mr. Bush, Michael Gerson, about Mr. Trump: “He lives in the eternal now — no history, no consequences.”

Mr. Trump’s refusal to accept some established facts is hardly new. From his belief in the guilt of five young men of color in connection with a savage attack on a white woman in Central Park in the 1980s, to his conviction that Mr. Obama was born in Kenya, he has carried on what amount to personal crusades in the face of established facts for much of his career.

The most noticeable new variation of that tendency that Mr. Trump has adopted as president is his penchant for giving the benefit of the doubt to authoritarian leaders with whom he has tried to develop personal or political relationships. That was most recently on display this week, when he said that King Salman of Saudi Arabia had assured him that the royal family had no role in the disappearance of the dissident journalist Jamal Khashoggi. The king, he noted, had given a “very strong” denial.

“Here we go again with, you know, you’re guilty until proven innocent,” Mr. Trump told The Associated Press on Tuesday. “I don’t like that. We just went through that with Justice Kavanaugh, and he was innocent all the way as far as I’m concerned.”

By Thursday, as the weight of the evidence of Saudi government complicity became hard to disagree with, Mr. Trump said that he believed that Mr. Khashoggi was dead, and that there could be “severe” consequences for Saudi Arabia.