One might think that happy presidential transitions are all alike, and that every unhappy presidential transition is unhappy in its own way. But both follow common patterns, and unhappy transitions can occur even when a long-serving and well-appreciated president is being succeeded by someone about whom the community has every right to be enthusiastic.

So—leaving aside those cases in which a departing president is, in effect, being ridden out on a rail, or the appointed successor is viewed by a significant segment of the community with feelings ranging from mild distrust to outright horror—let us ask: What makes for a happy transition and what does not?