Ms. Houlahan is among about 20 military veterans who have announced bids as Democrats to run for the House of Representatives next year. Democratic Party leaders are aggressively seeking former members of the military in hopes of bolstering their appeal among the sort of frustrated voters who elected President Trump — and winning back the 24 seats they need to regain the Republican-controlled House.

In many cases, those veterans say they feel called to run for public office in response to Mr. Trump himself, whose policies they see as a threat to the country’s values and security.

Democratic officials also see candidates with a military pedigree as an appealing contrast to entrenched, career politicians. And they believe that candidates with military service help the party counter Republican claims that Democrats are weak on national security.