Roosevelt virtually dictated the nomination of his presidential successor, William Howard Taft; after an African big-game expedition and a triumphal tour of European cities, Roosevelt returned (1910) to the United States and joined the campaign for the direct primary in New York. President Taft alienated the progressive Republicans headed by Robert M. La Follette, and the Republican party in 1912 was threatened with a split over the presidential nomination. The conservatives, however, controlled the Republican convention of 1912, and Taft was nominated for reelection.
Roosevelt led his followers out of the convention, organized the Progressive party—also called the Bull Moose party—and was nominated for President on this third-party slate. In the resulting three-cornered election he ran second to the Democratic candidate, Woodrow Wilson. Forced into retirement, Roosevelt denounced the policies of Wilson—whose attempt to secure a treaty awarding Colombia damages for the loss of Panama particularly enraged him. After the outbreak of World War I he attacked Wilson's neutrality policy; and when the United States entered the war he pleaded vainly to be allowed to raise and command a volunteer force. He died soon after the end of World War I.