Both parties are dumping money into this Hudson Valley district to notch a short-lived but symbolic victory in the last competitive race before the midterms. The winner will succeed Democrat Antonio Delgado for just a few months. But the messaging, turnout and margin of the contest will offer tea leaves into what lies ahead this fall in the battle for control of the House.

For Democrats, a win would offer proof that the party can translate their recent legislative victories and voter anger over the Supreme Court’s abortion ruling into tangible gains. After non-stop attention on their stalled policy agenda, internecine bickering and dire polling, Democrats are desperate to tell a different story.

“A win here would validate that the ground is shifting,” Pat Ryan, the Democratic nominee, said in an interview after a campaign event here with some three dozen supporters. “Democrats are really good at being hard on ourselves and we’ve been doing an awful lot of that. And sometimes you need to zoom out.”

“It will, maybe not reset, but I think certainly fundamentally reshape the trajectory,” he said.