3) But it’s also about a politician’s personal life.

This is the basic tension in both cases. There is a genuine legal issue, yet the underlying action is about a politician cheating on his wife, which is primarily a matter between the two of them. Moreover, that underlying action is not directly related to the core responsibilities of the president.

If Bill Clinton had been caught using the presidency to sell special favors — and I still suspect he did, given how he minted the presidency into a vast fortune after leaving office — that would have related directly to the duties of the office. The same would be true if Trump is found to be “colluding” with the Russians, though a smoking gun on that issue is looking more and more unlikely.

But if we’re dealing with a violation of law tied to an underlying action unrelated to the president’s core responsibilities, we have the same ambiguity as in 1998. It’s easy for one political party to insist upon the technicalities of the law and cry for prosecution, while the other party dismisses the whole thing as a petty witch hunt into the president’s private life.