During Taft's administration, a rift developed between Roosevelt and Taft, and they became the leaders of the Republican Party's two wings: progressives led by Roosevelt and conservatives led by Taft.
Progressives favored labor restrictions protecting women and children, promoted ecological conservation, and were more sympathetic toward labor unions.
They also favored the popular election of federal and state judges over appointment by the President or governors.
Conservatives supported high tariffs to encourage domestic production, but favored business leaders over labor unions and were generally opposed to the popular election of judges.

Cracks in the party began to show when Taft supported the Payne–Aldrich Tariff Act in 1909.
The Act favored the industrial Northeast and angered the Northwest and South, where demand was strong for tariff reductions.
Early in his term, President Taft had promised to stand for a lower tariff bill, but protectionism had been a major policy of the Republican Party since its founding.

Taft also abandoned Roosevelt's antitrust policy and fired popular conservationist Gifford Pinchot as head of the Bureau of Forestry in 1910.
By 1910, the split within the party was deep, and Roosevelt and Taft turned against one another despite their personal friendship.
The 1910 midterm elections proved to be rather rough for the Republicans, seeming to further cement the growing divide within the party.
During Taft's administration, a rift developed between Roosevelt and Taft, and they became the leaders of the Republican Party's two wings: progressives led by Roosevelt and conservatives led by Taft. Progressives favored labor restrictions protecting women and children, promoted ecological conservation, and were more sympathetic toward labor unions. They also favored the popular election of federal and state judges over appointment by the President or governors. Conservatives supported high tariffs to encourage domestic production, but favored business leaders over labor unions and were generally opposed to the popular election of judges.
Cracks in the party began to show when Taft supported the Payne–Aldrich Tariff Act in 1909. The Act favored the industrial Northeast and angered the Northwest and South, where demand was strong for tariff reductions. Early in his term, President Taft had promised to stand for a lower tariff bill, but protectionism had been a major policy of the Republican Party since its founding.
Taft also abandoned Roosevelt's antitrust policy and fired popular conservationist Gifford Pinchot as head of the Bureau of Forestry in 1910. By 1910, the split within the party was deep, and Roosevelt and Taft turned against one another despite their personal friendship. The 1910 midterm elections proved to be rather rough for the Republicans, seeming to further cement the growing divide within the party.
1912 United States presidential election