A strong “sound money” and high-tariff man, McKinley helped make the United States a world power. The Spanish-American War, commenced and ended upon his own terms, proved a trial run for American participation in World War I. Woodrow Wilson’s presidency might have ended on a better note had he followed McKinley’s example of including the opposition party in the peace negotiations.
McKinley understood the importance of international currency exchange - America was entering its peak industrial era, and needed a good trading medium. The tariff question is more complex: tariffs can be reduced or eliminated with those nations who do likewise, creating truly free trade. But against nations who impose tariffs, we must also levy, to create an equilibrium.
Mark Hanna was McKinley's campaign manager, both for his election and his re-election. Hanna and McKinley made a winning team:
In their two winning campaigns against the charismatic and populist “boy orator,” William Jennings Bryan, the two pioneered many of the techniques political consultants and their clients have employed ever since. As president, McKinley introduced them into the art of governance.
McKinley's victory in the Spanish-American War gave U.S. control over the Philippines. Difficult to manage, Roosevelt would eventually begin the process of spinning the Philippines off as an independent country (by 1935 the independence process would be almost complete, to be interrupted by WWII, and finalized in 1946).