In the large Democratic primary field of 24 presidential candidates, only Representative Tulsi Gabbard of Hawaii, Mayor Pete Buttigieg of South Bend, Ind., Representative Seth Moulton of Massachusetts and former Representative Joe Sestak of Pennsylvania are military veterans.

Mr. Moulton did not make the cut for the June debates and Mr. Sestak entered the race in late June.

Mr. Buttigieg and Ms. Gabbard both qualified, but they are debating on different nights. So each could benefit from being the only person on stage who can wield military credentials.

The background