Roosevelt's plan to convince Hoover to run for the Democratic nomination fell through after Hoover publicly declared himself to be a Republican, but Roosevelt nonetheless decided to seek the 1920 vice presidential nomination. After Governor James M. Cox of Ohio won the party's presidential nomination at the 1920 Democratic National Convention, he chose Roosevelt as his running mate, and the party formally nominated Roosevelt by acclamation. Although his nomination surprised most people, Roosevelt balanced the ticket as a moderate, a Wilsonian, and a prohibitionist with a famous name. Roosevelt had just turned 38, four years younger than Theodore had been when he received the same nomination from his party. Roosevelt resigned as Assistant Secretary of the Navy after the Democratic convention and campaigned across the nation for the Cox–Roosevelt ticket.