What was the source of conflict between the Federalists and the Anti-Federalists?

The Federalists were in favor of ratifying the Constitution because they wanted a strong central government; the Anti-Federalists were opposed because they supported decentralized power and greater individual and States' rights.

The Anti-Federalists in some states had enough power to force the Federalists to compromise by withholding their ratification until the Federalists agree to add the Bill of Rights. Eventually, all thirteen original states ratified the Constitution.