What accounts for the "new" 1818 Connecticut Constitution that repudiated the theocracy of the state and disestablished the Congregationalist Church? The answer is proof positive of Professor Richard Kay's proposition that a constitution, representing the foundation of legal system, is not based on law, but rather on politics, economics, and morality.
Connecticut was one of the last American states to separate church and state, and to provide for religious toleration. The 1818 religiously-tolerant Constitution resulted from three causes. First was the collapse of the political mainstay of the Congregational Church, the Federalist Party, which never recovered public support after sponsoring the Hartford Convention 1814-1815, where New England delegates advocated secession from the United States then engaged in the War of 1812. Second, was the small but growing number of non-Congregationalists in Connecticut, mostly Episcopalians, Methodists, Baptists, and Quakers from neighboring New York, Massachusetts, and Rhode Island, who became the foundation of a new political party, the Toleration Party, advocating freedom of religion, e.g., the right to found independent churches and no longer financially support the then-dominant Congregational Church. Third, was a division within the Congregational Church itself where a liberal wing, notably Unitarians and Universalists, openly challenged Calvinist doctrines and were willing to join the Tolerationists.
The 1818 Connecticut Constitution, recognizing the right of some though not all non-Congregationalist religions to practice, was the first step to what is now, two centuries later, a religiously tolerant state. Indeed, other faiths, including Catholics and Jews, each out-number Congregationalists in Connecticut, who now total only about two percent of the state's population
Janis, Mark Weston, "Connecticut 1818: From Theocracy to Toleration" (2021). Faculty Articles and Papers. 610.