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
1920 Democratic National Convention
1920 Democratic National Convention
Franklin D. Roosevelt