What happens to candidates’ delegates when they drop out?

In the 48 hours after former vice president Joe Biden won a dominant victory in the South Carolina Democratic presidential primary, two of his competitors for the party’s nomination suspended their campaigns. Both Sen. Amy Klobuchar (Minn.) and former South Bend, Ind., mayor Pete Buttigieg joined Biden in Texas on Monday evening to offer him their endorsements before the state’s primary on Tuesday.

Those endorsements were important, though the effects are hard to evaluate at the moment. What may be more important are the 33 delegates that Buttigieg and Klobuchar...