Final answer:
In the 1912 presidential election, Theodore Roosevelt ran as the candidate of the Progressive Party, also known as the Bull Moose Party, based on his doctrine of New Nationalism.
Step-by-step explanation:
In the 1912 presidential election, Theodore Roosevelt ran as the candidate of the Progressive Party, also known as the Bull Moose Party. This was a new political party that Roosevelt formed after the Republican Party chose William Howard Taft as their candidate. Roosevelt's campaign was based on the principles of his doctrine called New Nationalism, which focused on creating a more powerful federal government to regulate corporations and the economy in the public interest.