It is widely accepted that an atheist or an agnostic could not be elected president today. According to Franklin Steiner, many of our early presidents were irreligious to varying degrees, but none openly professed atheism.
However, during the past hundred years, presidents have found it politically necessary to at least profess Christianity. I have no factual basis for doubting any one of them, but it seems likely that at least some of them were essentially non-religious, while making an outward show of piety for political reasons. Below the orange squiggle I will make my case that this is not good for the country.
I think it is unfortunate that the electorate abhors atheists. It would be reasonable to accuse me of bias (I am an atheist), but I think there are objective reasons why non-believers would make better presidents than devout believers.
The reasoning is fairly simple. An atheist would have no religious dogma to cloud his or her approach to public policy. One need look no further than the current crop (Did I use the wrong vowel?) of Republican candidates to see the danger. If elected, Rick Santorum has made it clear--at least to this observer--that his presidency would be faith based. This means an agenda that is opposed to abortion, contraception, LGBT rights, stem cell research, teaching evolution, and friendly towards prayer in schools, posting the ten commandments, faith based initiatives, vouchers for religious education--in a word, his presidency would be a step towards theocracy. GWB started this trend (stem cell research, faith based initiatives) and Rick Santorum would surely advance it. Newt Gingrich and Ron Paul seem only slightly less batshit crazy inclined to govern religiously. What about Romney? His Mormon faith is evident by the fact that he tithes, but beyond that it is unclear how his religious beliefs would affect public policy. I don't know enough about Mormonism to bring up specific concerns; let's just say I'd be worried.
This Wiki article cites a poll that says 58% of Americans pray at least weekly, which suggests to me that something like 40% are more or less indifferent about religion. Only 9% say that religion is the most important thing in their lives. (Most of these 9% were Republican candidates at one time or another. :-))
To illustrate, suppose we want to find the best referee for the Super Bowl. Do we look for a lifelong Giants fan or a strong Patriots fan? No, we look for somebody who has no emotional stake in the outcome. If I were in charge of hiring football officials, I would simply disqualify any applicant who was an enthusiastic fan of any team.
Likewise, I think we would be wise to choose a president from the 40% who do not actively practice religion on an everyday basis. I would think that an atheist would be an ideal candidate, but we all know that today an atheist would be unelectable.
An atheist would not ask "Is a fertilized egg a person?" An atheist would not dream of banning liquor sales on Sunday. An atheist would not look in the Bible to decide on the right curriculum for a high school biology class. An atheist would not ask "Does this bill agree with my personal morality?" Rather an atheist would / ought to ask "What is best for the country as a whole?"
The religious far right is plainly obsessed with sexual and reproductive issues, and tends to legislate on the basis of their personal morality. With good reason, we see this as a war against women. It seems that there is always a controversial bill in front of some state legislature that oppresses women; this is a fact of the political landscape.
If we ask the question "What is best for society?" we would naturally tend to favor laws that discourage population growth. The far right consistently favors laws that tend to encourage population growth; any sexual behavior that tends to limit population growth is strongly disapproved. In their minds, reproduction is not a scientific or medical issue, it is a religious issue--and therefore a governance issue.
This atheist has a different view. I know that many Kossacks are believers, and it is not my intention here to proselytize for atheism nor to criticize theists. But I certainly hope that all Kossacks oppose the theocracy that the religious right would like to impose upon us.