During presidential scandals, members of the media often speak of the Iran-Contra affair. I’m not sure they really understand it.

In retrospect that scandal was distinguished by two central, shaping characteristics. First, it was different from other scandals in that its genesis wasn’t low or brutish. It wasn’t about money, or partisan advantage, or sex; it was about trying to free American hostages in the Mideast, and attempting to pursue a possible, if unlikely, foreign-policy advance. It had to do with serious things. Second,...