It was this weekend in 2012 that I went to a Halloween party wearing a quite realistic-looking Joe Biden mask. After about an hour, people said it was too spooky and asked me to take it off. When the Obama presidency ended, I threw the Biden mask away, assuming I’d never need it again. Wishful thinking is always a mistake.

With Halloween in the air, it’s the right moment to discuss the central role played in presidential politics by bogeymen—creatures conjured to distract and scare the citizenry. In politics, the bogeyman...