Poletti served as lieutenant governor of New York from 1939 to 1942. He lost his bid for reelection in 1942, as did gubernatorial nominee John J. Bennett Jr.. In December, Lehman resigned as governor in order to accept an appointment with the United States Department of State; Poletti succeeded to the governorship and served the final month of Lehman's term. After leaving office, Poletti served in World War II, initially as a special assistant to the Secretary of War, and then in the United States Army as a Civil Affairs officer responsible for rebuilding and restoring democracy in Italy following its liberation by the Allies.