Men of faith have made excellent elected persons in this country before...let me start there, because it's true. Religious faith, in itself, is not a sign of mental instability, stupidity, ignorance, dishonesty, malice, bigotry, or any other impediment to participation in our government.
Religious faith is also not a guarantee of sanity, intelligence, knowledge, wisdom, fairmindedness, honesty, goodwill towards all, or any other virtue necessary for governance.
Religious faith can be associated with a deep commitment to the rights and privileges our Constitution grants to all citizens...or it can be associated with a deep commitment to privileging one religion over others, attempting to impose one religion's beliefs and practices on those who do not share the same beliefs or agree with those practices.
Our Constitution is supposed to guarantee religious *freedom*...the right of each citizen to choose the kind, and degree of involvement (from zero to 100%) of religious belief and practice *so long as that practice does not infringe on the rights of those whose beliefs are different.* The government is forbidden to privilege any one religion--to promote one over the others, to impose on those with different beliefs the rules of any one. It was intended to be secular, even when the positions of government were held by persons of religious faith--that is the only way to guarantee the rights of all in a society where not all hold the same beliefs.
It was written that way because the men who debated and wrote the Constitution and the Bill of Rights had experienced--or their parents had experienced--religious wars, both in the countries they came from and here as well. The English Civil War. The wars of the Reformation and Counter-Reformation all across Europe. They knew that unless the Puritans of New England and the Catholics of Maryland and the Dutch Reformed of New York and the Anglicans of Virginia and the Quakers and Calvinists of Pennsylvania agreed to set aside their individual disagreements for the common good--to live and let live--this new nation could not even begin to come together. Only a secular government--a government that did not sanction any one of them above the others--could work.
Every citizen could believe what he or she chose...but could not impose his or her beliefs on others outside his or her own group. Where citizens agreed on a policy that might have had its origin in religion (murder is wrong; theft is wrong; etc.) such laws could be made--because they were not just religious laws, but practical and reasonable rules for living together that atheists, agnostics, and religious believers could all agree on.
But there are beliefs which, legal in themselves under this protection, unfit someone for public office, especially at the national level. Anyone who sincerely believes that he or she is commanded by their deity to convert others, or impose on others their beliefs and practices, to appeal to or quote their religion's scriptures, runs into a problem the moment he or she is elected to public office, or is appointed as a judge or an officer in the military. These positions require one to swear, under oath, that the candidate will "uphold and defend" the Constitution of the United States. That Constitution includes the proviso that no religion will be established by the state, that no religion will be privileged over another. And if someone thinks the Constitution is wrong in so saying--believes that his/her religion requires trying to force the nation to behave according to one religion's rules--then that person cannot take that oath of office honestly.
Note well: that belief is legal--within the private sector. But it is incompatible with the duty to uphold the Constitution. The individual who holds such a belief must either choose not to take that oath--not to run for office, not to become a military officer, not to become a judge--or choose to lie, to say the words but intend to undermine the Constitution he or she has just sworn to uphold.
The honest person will see that, and step back. When a religious zealot does not step back, you know you're looking at a dishonest religious zealot and such persons (however charming, personable, and apparently reasonable in other ways) is a serious, clear, and present danger to the common good of a nation that has stood for religious freedom for over two centuries.
It does not matter what your religious beliefs are. What matters here is that you grasp the underlying problem: if someone sincerely and deeply believes that their deity trumps the Constitution, *and* believes that he/she has a duty to convert others and make others conform to his/her beliefs and practices, then he/she cannot be honest when taking the oath of office (or for that matter the commissioning oath of officers in our military.) Someone cannot at the same time uphold, protect, and defend the Constitution...and be planning to subvert it.
We do not need a religious zealot as President. I would say the same of *any* religious zealot, but since the country has leaned way over on the side of Christian fundamentalism (a very controlling group of beliefs) in the past >10 years, with the help of the Administration in the past 8, I am particularly concerned that no Christian fundamentalist who thinks he/she has a mission to turn this into a theocracy be elected this time.
What we need is someone who--whatever their own faith and however they live it--will respect the rights of every individual citizen of every color and every creed (including the creed of disbelief), will not demonize segments of society he/she does not agree with...someone who understands, and will practice, the need to create unity and not division. Someone who respects the role of religion in peoples' lives, but is committed to a secular government, holding the line against the zealots of every faith. (And someone who isn't relentlessly anti-intellectual...that would be nice too. Someone who is willing to learn and can think straight...)
As for me, I'm a Christian...the other kind. The kind who thinks "feed the hungry, clothe the naked, house the homeless, visit the sick and imprisoned..." will keep me busy enough to let other people go their own way (unless they don't want to let me go mine, and others go theirs, and in that case...I'm firmly behind the Constitution.)