Trust me, though: He has not been sweated before like he would be in a special-counsel interview. It would be a mistake to assume that because Mueller’s team overflows with Democratic partisans, they are just like the political hacks Trump jousts with all the time. These particular prosecutors are extraordinarily good at what they do. They are not going to be cowed or charmed. If Trump agrees to speak to them, he will not be able to control the direction of the questioning; and if he loses his cool and says things that are dubious or flatly untrue, they will clean his clock.

In other words: Trump the man could walk out of an interview with Mueller in real jeopardy, despite walking into it in nothing more than a bad mood. Which brings us to our other client: Trump the president.

A president of the United States should never be the subject of a criminal investigation, and should never be asked to provide testimony or evidence in a criminal investigation, in the absence of two things: solid evidence that a serious crime has been committed and a lack of any alternative means to acquire proof that is essential to the prosecution.

There is a simple reason for this: The awesome responsibilities of the presidency are more significant to the nation than the outcome of any particular criminal case.