Final answer:
Teddy Roosevelt ran for president as the candidate of the Progressive Party, known as the Bull Moose Party, in 1912 after not getting the Republican nomination.
Step-by-step explanation:
Teddy Roosevelt of the Progressive Party, also known as the Bull Moose Party, was the most successful minor-party presidential candidate in history. This unique moment in U.S. history saw a former president running for office against both an incumbent and a future president. When Roosevelt, who was then a former president, did not secure the Republican nomination in 1912, he and his followers separated from the Republican Party to form the Progressive Party. He aimed to win the presidency through this new party, capturing many votes though ultimately not winning the election. The Progressive Party became colloquially known as the Bull Moose Party following Roosevelt's remark that he was 'as strong as a bull moose' after surviving an assassination attempt.