Item 1: Obama's mother was nonreligious. She raised him, teaching him about many different religions. The best predictor of a person religious views is that of his peers:
The best predictors of youth religiosity were ethnicity and peers' church attendance during high school. Other predictors were, in order of decreasing magnitude: residence in the south, gender, religious schooling during childhood, maternal religiosity, church attendance during childhood, the importance mothers placed on childhood religious training, and an interaction variable identifying religious mothers who were very supportive. These analyses attest to the primacy of religious role models in the development of youth religiosity.Obama talked about his parents in 2006:
And I speak with some experience on this matter. I was not raised in a particularly religious household, as undoubtedly many in the audience were. My father, who returned to Kenya when I was just two, was born Muslim but as an adult became an atheist. My mother, whose parents were non-practicing Baptists and Methodists, was probably one of the most spiritual and kindest people I've ever known, but grew up with a healthy skepticism of organized religion herself. As a consequence, so did I.Item 2: Obama has spoken out against religion, stating that "We are no longer just a Christian nation."
Item 3: Obama is really smart and very ambitious. There does exist a anti-correlation between being smart/educated and religious. Further, he of course knew that it is impossible for an atheist to get elected, and could thus early on have joined a church in order not to ruin his chances at conception.
In conclusion, let me say that none of this prove anything, and that I acknowldge that Obama may in fact really believe in God. He is a member of United Church of Christ, which may indicate that he is sincere in his belief (more so than if he were a member of another Protestant denomination, though I have no personal knowledge of the differences between the various congregations). I don't know. But if I had to guess, I'd say that this is the closest America has ever been to a non-believing President yet (but see comments below).