During the ratification debate, George Mason called himself a Republican and decried the nationalists for calling themselves “Federalists.” Elbridge Gerry later said that there really had been two parties during the ratification debate “rats and anti-rats.”
The first party under the US Constitution was the Republican Party — if we want to call it a party. At least, political scientists by the early 1990s had identified a couple of dozen members of the House who consistently voted with James Madison across a wide range of issues. This group congealed into a party. Seeing how they were organizing themselves, Alexander Hamilton organized his Federalist Party in support of the Washington Administration.
Historians of the 1790s most commonly call the Madison-Jefferson party the Republican Party, even though it might more accurately be called a proto-party. More confusing for students is that the party Hamilton organized took the same name as proponents of ratification had used only a few years before.