B. Theodore Roosevelt
In the 1912 election, the Republican Party was divided. Its conservative wing supported President William Howard Taft for reelection. Theodore ("Teddy") Roosevelt, who had been President from 1901-1909, led the progressive wing of the Republicans. Ultimately, Roosevelt and his supporters objected to the nomination of Taft as the Republican candidate, and formed a 3rd party, the Progressive Party, with Roosevelt as their presidential candidate. The Progressive Party was nicknamed "The Bull Moose Party," a reference to how Roosevelt described himself.
Roosevelt won 27% of the popular vote; Taft received 23% of the popular vote. Democratic candidate Woodrow Wilson got 42% of the popular vote and carried 40 states to win the Electoral College vote handily.