Actually, to an atheist like me, Obama looks VERY religious. He is also very protestant in his style - something that leaves me personally quite cold. Of course, there are many other politicians who, probably, are quite atheist, but wouldn't fess up, but he doesn't seem to be one of them.
I'm intrigued. What gives it away?
Obama's speaking style is very "black preacher"-ish in its pitch and timbre; he's obviously had a good deal of exposure to that rhetorical style.
Bill Clinton might have been an agnostic/atheist, maybe even Dubya, but that would be one of the most epic trolls of all time, I don't think you could actually go for so long without breaking character.