Article 6, Section 3 of our Constitution reads as follows:
Section 3. 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.
The meaning of this section is clear and has never been legally disputed. In summary …
All government officials, elected or appointed, must swear an oath to support the Constitution of the United States. However, that oath need not be religious in nature, and the government cannot require its officials to pass any test of religious affiliation to take office. The ban on religious tests was included to ensure that the U.S. government would remain secular.
Note that this has nothing whatsoever to do with what qualifications any individual or party feels are appropriate for any office. I can quite properly believe, for example, that no person who isn’t fluent in English should be President. I can say that I wouldn’t support anyone who isn’t a Christian, or anyone who is over 70 years of age, or any other rule that seems sensible to me. None of that violates the Constitution in any way. You may think that I am making a mistake, but you have absolutely no right to deny me my choice or my beliefs.
What Dr. Ben Carson said about not being willing to support a Muslim for President, or his clarification that he meant one who doesn’t renounce Sharia Law, may have been politically inept but it violates no law nor any principle of our Constitution. Calls for him to end his candidacy on this basis are entirely inappropriate. If you disagree with him, vote for someone else. In fact, even bringing up this clause of our Constitution in the context of his remarks, as have many commentators, demonstrates an abysmal understanding of its meaning and intent.
Actually, eight states have clauses in their Constitutions that either require state officeholders to profess particular religious beliefs or protect those who do. They are not enforced because they certainly couldn’t withstand a federal constitutional challenge.