After having already served two terms as President and taking a four-year hiatus, Teddy Roosevelt attempted to win the Republican nomination for the 1912 campaign from then-President William Howard Taft, whom he hated. Failing that, he pulled his delegates from Republican convention and formed the Bull-Moose Party, naming it after an animal that is slightly larger than Taft's fat ass.
The creation of this offshoot party caused endless infighting amongst those loyal to the Republicans and those loyal to Roosevelt, effectively splitting the vote. In the end, both parties (and the American people) lost, as Democrat Woodrow Wilson won the election.
Teddy eventually returned to the GOP, and Republicans have never fought amongst themselves again.
Tags: Theodore Roosevelt, Third-Party Poopers, William Howard Taft