The work necessary to identify the vast majority of these men as Christians has to ignore many things, primary of which is that they were from colonial and state theocracies. Interestingly, the only sect supporting full religious liberty and separation of church and state, the Baptists, had no members at the Constitutional Convention, while 80% lived in states/colonies that mandated certain religious affiliation.
Of the 55 people at the Convention, 70% were affiliated with Establishment churches or recently abolished establishment churches (Virginia’s disestablishment took place in 1786)
Which of us now would argue that affiliation with state established churches equals true Christianity? But such is the argument needed to make the case that the majority were Christian.
The second issue is that to make the majority case, one has to expand the list of founders to include a vast number of people who were not the true leaders. Most historians list seven to nine people as the leaders of the Founding, which includes the first five Presidents. When we look a t this small list, we see only one who might be called an orthodox Christian (see list below).
Maybe these nine were more outspoken about their beliefs than the others or maybe they were just different or maybe we just know more about them, but it cannot be argued that they were the primary movers.
Picture is from here
Deism: The belief, based solely on reason, in a God who created the universe and then abandoned it, assuming no control over life, exerting no influence on natural phenomena, and giving no supernatural revelation.
Unitarianism is named for its understanding of God as one person, and contend that main-line Christianity does not adhere to strict monotheism as they do, maintaining that Jesus was a prophet and in some sense the “son” of God, but not God himself.
Calling either of these Christian is a stretch. Sort of like calling Muhammad or Einstein a Christian. You can do it, but doing so does not make it so.
The Founders Religions
George Washington (first in the nation)was baptized as an infant into the state-supported Episcopal/Anglican church; rarely attended church after 1770 he never took communion, was often called a Deist.
John Adams (first VP, and 2nd President) was a non-Trinitarian Unitarian. To be very clear, a Unitarian denies the divinity of Jesus, but accepts there is a God.
Thomas Jefferson (writer of the Declaration of Independence and 3rd President) was a pure deist who many Christians of his day called him a heretic, infidel or atheist.
James Madison (so-called father of the Constitution and 4th President) was a deist who sometime attended the state-supported Episcopal/Anglican church, but strongly opposed the efforts of church leaders to extend colonial theocracy to the new nation.
John Jay (1st Chief Justice) was an Anglican and the only one of the Primary Founding Fathers who could be thought of as an orthodox Christian.
Alexander Hamilton (1st Secretary of the Treasury) was not a member of a church until after 1801, but did use religion for political gain
Benjamin Franklin (author and general all around good guy, the founder most would choose to have a beer with) was raised Episcopalian but as an adult, was a Deist.
James Monroe (5th President) was a Deist who on occasion attended the Episcopal Church.
Thomas Paine (philosopher and pamphlet publisher) was an unabashed Deist who held Christianity is disdain.
I am a Christian (an unorthodox one, but still) and can see the vestiges of Christianity in the laws of our nation, but those things are not solely Christian, and o0ne can pick as the source many other belief systems.
The miracle of the Constitution is that the leaders at the time kept theocracy out of the law and made the first secular nation.