As a someone who has done a bit of research around this topic, let me throw in my two cents:
A point of clarification- It was not until 1925 that lawmakers and judges “incorporated” the Bill of Rights onto the states. In other words, during the 19th century the Constitution only described what the federal government could or couldn’t do to citizens. Therefore states were free to have established religions, and some did, under the US Constitution. This was very problematic after the passage of the 14th amendment, but was not clarified until 1925. Today, we interpret the Bill of Rights as applying to state and local government as well, but that just wasn’t the case when the establishment and test clauses were added to most state constitutions.
As for the oath and test clause careful reading was applied to that… Oath to Constitution is required for State and Federal Offices, no test is allowable for federal office of employees.
Article 6: “The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States.”
Under the US was interpreted as federal, if they had wanted to end test clauses they would have included a several states clause like they had for the oath. It was a contentious point, and no one was willing to tell states to eliminate their (sometimes previously existing) test clauses and established religions. The Constitution at the time of Ratification did not claim to eliminate all test clauses or established religions, just federal ones- and in fact left some intact and some were included in newer state constitutions of the 19th century with out challenge. They did not “break the Constitution,” the Constitution changed around them.
As far as the bigger debate about the nature of American freedom of religion vs dominion-ism / “Christian Nationhood” I think this debate tends to be oversimplified. Surely the “Founding Fathers” were “mostly Deist types” and the Constitution stands out for how little it says about religion- and the Confederate Preamble would “fix” that a few years later- but to say somehow that means “the US is a Secular State” is also overreaching. I am not trying to put words in anybodies mouth, but I have seen this debate in many forms.
1. No, America was not founded as a Christian Nation in any Theocratic sense.
2. It (The federal Constitution) was founded to try to create freedom of religion, and I think also freedom from religion, but that point is more difficult to pin down.
3. The Constitution is but one battle line in this culture war, and marks merely a starting point for the evolution of this debate. There was a significant backlash against the Constitution as “Godless” and many state legislatures enacted test clauses in new state constitutions to remedy what they saw as a defect. As mentioned, the South in particular revolted against this and railed against it, culminating in its CSA constitution, here is its preamble:
“We, the people of the Confederate States, each state acting in its sovereign and independent character, in order to form a permanent federal government, establish justice, insure domestic tranquillity, and secure the blessings of liberty to ourselves and our posterity — invoking the favor and guidance of Almighty God — do ordain and establish this Constitution for the Confederate States of America.”
The David Bartons are terribly wrong (historically) when they argue the US was created as a Christian Nation, but I think it is also a mistake to look at the Constitution and declare clear victory for freedom of religion and especially not for secularism- that is a battle that continued in the early national period, the Civil War, Reconstruction, 1920s, 1950s, and today- Our institutions have evolved and continue to evolve. The Constitution is not the only battle line, it was the first of many. In fact, despite this clear set back, in many ways it seems that the dominionists are more in control now than they were in 1789.
I guess what I am trying to say is do not rest too comfortably in your knowledge that the founding fathers wanted x or y… The reality is no presidential candidate dares to run as an atheist. There may be no test clause in the Constitution, but ask your self if its not a defacto requirement.