The bitter battle between Theodore Roosevelt and his successor William H Taft led to the formation of a third party, called Progressive or Bull Moos Party. This split from the Republican party resulted in the election of the Democratic contender, Woodrow Wilson, in 1912.
President Roosevelt groomed and mentored Taft to be his successor in the White House. Taft got elected for president in 1908 but his administration was rather conservative, and in direct conflict with Roosevelt's progressive version.
Disappointed with Taft, Roosevelt ran for president again in 1912 but he could not find enough supporters among Republicans. This resulted in the split and the forming of a new political party, the Progressive.
I the end, and as the result of the split, the Democrat Woodrow Wilson won the election.
