Roosevelt had served as president from 1901 to 1909 , and Taft had won the 1908 Republican presidential 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 . Roosevelt 's Progressive Party was nicknamed the Bull Moose Party after journalists quoted Roosevelt saying that he was " feeling like a bull moose " on the campaign trail shortly after the new party was formed . Backed by William Jennings Bryan and other progressives , Wilson won the Democratic Party 's presidential nomination on the 46th ballot , defeating Speaker of the House Champ Clark and several other candidates . Meanwhile , the Socialist Party renominated its perennial standard-bearer , Eugene V. Debs
1912 Republican National Convention
1912 Republican National Convention
1912 United States presidential election