Roosevelt left office in 1909. He had selected Taft, his Secretary of War, to succeed him as presidential candidate and Taft easily won the 1908 presidential election. Roosevelt became disappointed by Taft's increasingly conservative policies. Taft upset Roosevelt when he used the Sherman Anti-Trust Act to sue U.S. Steel for an action that President Roosevelt had explicitly approved. They became openly hostile and Roosevelt decided to seek the presidency. Roosevelt entered the campaign late as Taft was already being challenged by Progressive leader senator Robert La Follette of Wisconsin. Most of La Follette's supporters switched to Roosevelt, leaving the Wisconsin senator embittered.