One reason voters like to see candidates debate is that, at least in more conventional campaigns, these occasions sort out the thinkers from the poseurs, the candidates that have substance from those who are empty vessels making noise.

The public does not necessarily want to elect a wonk who can fully describe the workings of, for example, the Department of Veterans Affairs. But they do want someone who demonstrates a grip on what that lamentable agency’s problems are and has a realistic plan to solve them.