Accomplished people lacking inner strength can’t resist the compromises necessary to survive Mr. Trump and that adds up to something they will never recover from. It takes character like Mr. Mattis’s to avoid the damage, because Mr. Trump eats your soul in small bites.

It starts with your sitting silent while he lies, both in public and private, making you complicit by your silence. In meetings with him, his assertions about what “everyone thinks” and what is “obviously true” wash over you, unchallenged, as they did at our private dinner on Jan. 27, 2017, because he’s the president and he rarely stops talking. As a result, Mr. Trump pulls all of those present into a silent circle of assent.

Speaking rapid-fire with no spot for others to jump into the conversation, Mr. Trump makes everyone a co-conspirator to his preferred set of facts, or delusions. I have felt it — this president building with his words a web of alternative reality and busily wrapping it around all of us in the room. ...

You feel this happening. It bothers you, at least to some extent. But his outrageous conduct convinces you that you simply must stay, to preserve and protect the people and institutions and values you hold dear. Along with Republican members of Congress, you tell yourself you are too important for this nation to lose, especially now...