Roosevelt had served as president from 1901 to 1909, and Taft had won the 1908 Republican president nomination with Roosevelt 's support. Displeased with Taft 's actions as president, Roosevelt challenged Taft at the 1912 Republican National Convention. After Taft and his conservative allies narrowly prevailed at the Republican convention, Roosevelt rallied his progressive supporters and launched a third party bid. With the support of William Jennings Bryan and other progressives, Wilson won the Democratic Party 's presidential nomination on the 46th ballot. Meanwhile, the Socialist Party renominated its perennial standard - bearer, Eugene V. Debs.
who ran as the socialist candidate for president in 1912
Eugene V. Debs