 In 1914, Curtis was elected to Kansas's other Senate seat by popular vote and was re-elected in 1920 and 1926.In total, he served from March 4, 1915, to March 4, 1929, when he resigned to become Vice President.During his tenure in the Senate, Curtis was President pro tempore, Chairman of the Committee on Expenditures in the Department of the Interior, of the Committee on Indian Depredations, and of the Committee on Coast Defenses; and Chairman of the Republican Senate Conference.