During the 2016 campaign, I received a phone call from an influential political journalist and author, who was soliciting my thoughts on Donald Trump. Trump’s rise in the Republican Party was still something of a shock, and he wanted to know the things I felt he should keep in mind as he went about the task of covering Trump.

At the top of my list: Talk to psychologists and psychiatrists about the state of Trump’s mental health, since I considered that to be the most important thing when it came to understanding him. It was Trump’s Rosetta stone.

I wasn’t shy about making the same case publicly. During a July 14, 2016, appearance on C-SPAN’s Washington Journal, for example, I responded to a pro-Trump caller who was upset that I opposed Trump despite my having been a Republican for my entire adult life and having served in the Reagan and George H. W. Bush administrations and the George W. Bush White House.

“I don’t oppose Mr. Trump because I think he’s going to lose to Hillary Clinton,” I told Ben from Purcellville, Virginia. “I think he will, but as I said, he may well win. My opposition to him is based on something completely different, which is, first, I think he is temperamentally unfit to be president. I think he’s erratic, I think he’s unprincipled, I think he’s unstable, and I think that he has a personality disorder; I think he’s obsessive. And at the end of the day, having served in the White House for seven years in three administrations and worked for three presidents, one closely, and read a lot of history, I think the main requirement for president of the United States … is temperament, and disposition … whether you have wisdom and judgment and prudence.”