Answer:
The supporter of federalism that warned people about the dangers of political parties was George Washington.
Explanation:
Like all revolutionaries, Washington hated political divisions and was an enemy of what we now call political parties. The revolutionary principles, the "spirit of 76", should be unique and accepted by all. But, by clearly leaning towards a strong federal power, he faced supporters of the primacy of the states. These, led by Thomas Jefferson, began to organize giving rise to a political faction that was soon known as anti-federalist, as opposed to the others, who were federalists. As the name had a negative connotation they preferred to be called "Republicans" and later, "Democrats": they are the Democratic Party of our day, the oldest political party of those that exist today. It cannot be said that Washington was the founder of the political parties - the merit, if any, belongs to Jefferson - but he was the cause of their creation.
