What source was instrumental in supporting the constitution during the ratification debate? a. anti federalist papers. b. two treaties of government. c. common sense. or d. federalist papers.

The correct answer is (D).  The Federalist Papers were highly instrumental in supporting the U.S. Constitution during the ratification debate.  These 85 papers - which together form the Federalist Papers - were incredibly important in terms of arguing on behalf of the ratification of the Constitution and serve, even today, as the ultimate explanations in terms of the meaning of the Constitution.