Final answer:
William Howard Taft is considered the least progressive president among Roosevelt, Taft, and Wilson, due to his failure to significantly reduce tariffs with the Payne-Aldrich Act and his conservative handling of public lands and conservation issues.
Step-by-step explanation:
The least progressive president among the three considered progressive - Theodore Roosevelt, William Howard Taft, and Woodrow Wilson - was William Howard Taft. Despite Taft's initial campaign promises to lower tariffs, key legislation like the Payne-Aldrich Tariff Act of 1909 failed to significantly reduce tariffs and, in many cases, actually raised them due to amendments by conservative Republicans. Taft’s reluctance to challenge the conservative majority in his party and his backing down on tariff reductions, as well as his conservative stance on the exploitation of public lands, including the Alaska land deal controversy, made him appear as the least progressive. He is notably remembered for firing Gifford Pinchot, a staunch conservationist, which hurt his standing among progressives and conservationists, despite his eventual conservation achievements.