In America, any person, even a presidential wannabe, is free to practice whatever religion he or she chooses. Constitutionally, it would seem that a candidate is free to mention his or her beliefs, and members of the voting public are equally free to use those religious beliefs as a Ouija Board pointer to help them pick a favorite.
When presidential candidates refer to their “faith,” though, they almost always use the word in the abstract. But in their private lives, they all do claim to practice a specific religion. It would be deceitful for candidates to claim that their faith is merely some amorphous belief in a fuzzy, non-sectarian supernatural being. No, for each candidate, his or her faith springs from a particular set of religious teachings, which conflict with the teachings of other religions. A candidate who professes faith is essentially endorsing one religion over others.
The implication of all the “faith” talk is that each candidate will, if elected, use his or her faith to influence presidential actions. Otherwise, why discuss faith at all?
But using a specific faith under which to govern may lead to a violation of the First Amendment. That amendment speaks only of the actions of Congress, not of the president. However, if Congress follows the policy recommendations of a president who uses his or her faith to help decide governmental questions, that Congress is endorsing the president’s religion — at the expense of others.
A president swears (or affirms — ha!) to “... preserve, protect and defend the constitution of the United States.” That Constitution clearly forbids lawmakers from establishing religion (Note: not a religion, but religion in general).
Some interpreters argue that an “a” is implied, and that Congress may legislate in a vaguely pro-religious way as long as it doesn’t support one belief system over another. But nobody except the most blatant theocrat believes that one religion should be favored. So the president, whoever it may be, must not allow Congress to be swayed by his or her own particular form of faith. If the president makes decisions based on that faith — a faith grounded in a specific religion — and urges legislators to implement such decisions, the president is acting contrary to an explicit Constitutional prohibition.
Therefore: For a candidate to make an implied promise that faith will play a part in his or her governmental decisions is tantamount to saying that he or she, if elected, will violate the Constitution.