Barbara Bush was a legendary figure in Trump’s own party. And neither President Obama nor President Bush would have had to worry about the foul memories and ill will stirred up by his presence.

Trump is a whole new, supersized kind of pariah: president non grata. He has made that many enemies, indulged in that much tactlessness and worked that diligently to consign apology and atonement to the dustbin of leadership.

Prince Harry and Meghan Markle are to be married in a week and a half, and decided not to invite major political figures, but imagine if they had wanted to. Obama would have been a logical inclusion, given that he and Harry have partnered in philanthropic work.

But Trump would have been unthinkable. In a past life, he repeatedly entertained questions from Howard Stern about whether he would have slept with Harry’s mother, Princess Diana. Yes, he said, although he once qualified that answer by saying that he would have insisted first that she take an H.I.V. test. It’s the gentlemanly thing.