Other forms: federalists
A federalist is someone who believes in the type of political system in which states or territories share control with a central government. Alexander Hamilton, one of the founders of the United States, was a federalist.
Canada and the U.S. both have federalist systems of government — individual states or provinces govern themselves, but they also unite with a federal government that has authority over the entire country. When it has a lower-case f, the word federalist describes someone who advocates this kind of system, while an upper-case F denotes a member of a specific political party.