The central domestic issues concerned government regulation of railroads and large corporations ("trusts"), the money issue (gold versus silver), the protective tariff, the role of labor unions, child labor, the need for a new banking system, corruption in party politics, primary elections, the introduction of the federal income tax, direct election of senators, racial segregation, efficiency in government, women's suffrage, and control of immigration. Foreign policy centered on the 1898 Spanish–American War, Imperialism, the Mexican Revolution, World War I, and the creation of the League of Nations. Dominant personalities included presidents William McKinley (R), Theodore Roosevelt (R), and Woodrow Wilson (D), three-time presidential candidate William Jennings Bryan (D), and Wisconsin's progressive Republican Robert M. La Follette, Sr.