In the months following the convention, he was a leading Anti-Federalist, along with Patrick Henry and George Mason, whose collective efforts led to the passage of the Bill of Rights.

In 1785, he was elected to the Confederation Congress by the Maryland General Assembly, but his numerous public and private duties prevented him from traveling to Philadelphia.

Martin believed the legislative branch should be unicameral, proposed limiting the standing army during peacetime, and argued that the Convention had exceeded its powers by creating a national government when they were sent to Philadelphia "for the sole and express purpose of revising the Articles of Confederation.

"[3] Martin served on the committee formed to seek a compromise on representation, where he supported the case for equal numbers of delegates in at least one house.

Failing to find any support for a bill of rights, Martin and another Maryland delegate, John Francis Mercer, walked out of the convention on September 3, 1787.

He was one of the most vocal opponents of slavery at the Constitutional Convention, denouncing it as "an odious bargain with sin" that was "inconsistent with the principles of the revolution and dishonorable to the American character.

George Washington and Benjamin Franklin had backed the change of direction of the convention, but, Martin said, we should not "suffer our eyes to be so far dazzled by the splendor of names, as to run blindfolded into what may be our destruction."

In an address to the Maryland House of Delegates in November 1787 and in numerous newspaper articles, Martin attacked the proposed new form of government and continued to fight ratification of the Constitution through 1788.

In the first case, Martin won an acquittal for his close friend Supreme Court Justice Samuel Chase in his impeachment trial in 1805.

By this time, detestation of Thomas Jefferson, his one-time decentralist ally, led Martin to embrace the Federalist Party, in apparent repudiation of everything he had argued for so strenuously.

An extended display of his eloquence and volubility appears in "Modern Gratitude in Five Numbers: Addressed to Richard Raynall Keene, Esq.