After the Continental Congress, Sam Adams returned to his home of Boston to try to restore order in an increasingly chaotic atmosphere. Massachusetts had long before fallen behind other states in forming a constitution and a stable form of self-government. By 1779, when a Constitutional Convention was called and both John Adams and Sam Adams were nominated as delegates, the state had already rejected one draft constitution. Sam Adams fell sick during the convention and all but one section of the constitution was written by John Adams. Article III, though, was written solely by Sam Adams. His Puritan underpinnings and reactionary religious feelings showed through as the article proclaimed that everyone would pay taxes to support the local Congregational Church, except Quakers, Baptists, and Episcopalians who would pay taxes to support their own church. All other sects would face a lengthy legal battle before they might be recognized. That section of the document survived until 1833. Adams also tried to establish a unicameral legislature, but that met with little support among the delegates. Nonetheless, as the Constitution of 1780 was adopted, Sam Adams welcomed the new government and marked the end of his days as a revolutionary. He now stood solidly behind the government. In 1781, Adams was elected president of the Massachusetts Senate. Later, as Daniel Shay advocated rebellion in western Massachusetts, Adams denounced the efforts and called him a traitor.

The move from the Articles of Confederation to the Constitution, though, caused Adams much concern. He fully believed that the United States were too large and had too many different needs to be adequately represented under a single government. Adams also wondered if the Constitution provided adequate protection for civil liberties, and his belief in natural law–the very basis for all of his revolutionary work–made him wary of any attempts to strengthen a central government. Adams remained silent on the issue until after he was elected to the Constitutional Convention as a Massachusetts delegate. The other delegates immediately recognized the danger Adams's opposition posed, and they cultivated and organized a vote among Boston workingmen and artisans–Adams's core supporters–to rebuke Adams for his anti-Constitution outbursts. They met in January 1788 and voted to support the new document and the ensuing government. The vote effectively muzzled Adams for the remainder of the debate. He seemed increasingly to have lost his "edge" and appeared to be drifting away from his former supporters–although he and Hancock had mended their friendship to fight against the Constitution together. Adams lost a key Boston election to a fellow Convention delegate that had supported the Constitution. It appeared from many respects that the age of Sam Adams was waning.

Adams now wished that America would be purified by its return to freedom and independence–that his Puritan ideals of a simple society would once again be made true. Unfortunately, the days of post-revolutionary America were ones filled with profiteers and speculators, hardly the saints, for whom Adams had hoped. Adams's troubles were just beginning. His old friend John Hancock, who remained bitter that Adams had not supported him for commander-in-chief of the American armies, had built up a solid political base in Massachusetts while Adams worked at the Continental Congress. In 1778, Adams received word that he had been reprimanded for his conduct by the Boston town meeting–a personal blow to a man who had led the town meetings for decades. And instead of electing a "pure" man to be the first governor of Massachusetts, perhaps Adams himself, the people elected Hancock–who partied and paraded through the city in victory and quickly doused any hope Adams held that the commonwealth might be returned to its Puritan roots.

Adams found his next fight in 1784 when young Bostonians founded the Sans Souci Club, and Boston's nightlife began to rival that of New York's. Rumors even swirled that the city might become home to a gambling club that allowed girls over the age of sixteen inside. Adams began writing editorials as vitriolic and sour as any he wrote during the period before the revolution. He hinted that the city would fall just as the mass orgies had once brought about the fall of Rome. The city could be corrupted so soon after it won its freedom and cleansed itself of the impurities of Britain. In 1792, Adams even attempted to have a traveling theater group jailed. Harvard students complained of his efforts as crusader of morals, and others charged he merely wanted to raise another mob. However, years of abuse had thickened Adams's skin, and he merely replied that "I know by their roaring I have hit them right."

Adams's popular spirit saw a brief reawakening in 1793 as the French Revolution erupted in Paris. After Hancock's death in 1793, Adams became the leader of the Jacobin faction of Massachusetts government, and the former revolutionary managed to hold on to enough of his late friend's supporters to be elected governor of the state. It appeared for a moment that Adams might launch a new revolution with Jacobinism as the new motto and spirit. French tricolors began to appear around Boston and gangs of Jacobin supporters roamed the streets in a throwback to the days of the Sons of Liberty. Now in failing health, Adams tried to attend as many celebratory dinners as he could. His opponents screamed that he appeared more like a French diplomat than the governor. However, Adams's influence steadily waned through the 1790s, and by 1795, his opponents managed to remove his supporters from office. In 1796, John Adams ran for the presidency on a pro-Constitution ticket and when Sam Adams failed to win selection as an elector opposed to his cousin, he announced he would step down as governor.

In his final years, Adams was but a shell of his former self. The country had gone solidly in favor of the Constitution and palsy had robbed Adams of the ability to write. Adams kept hoping that the fever of the successful French Revolution would sweep across the United States; the Father of America died in 1803, disappointed.