None of us can make windows into men's soul so only he can truly know. But there is a general tendency among certain people to assume that all christians are either firebreathing literalists or don't really believe it, and that's unfair and rather silly. There are far more sincere christians who don't hold, say, the views of Rfayette than do. And after reading his eulogy for Clementa Pinckney, I do find it difficult to believe that Obama is lying about the whole christian thing, because that speech is a very christian work.
I agree completely. I have no reason to doubt Obama's word on this, and neither does anyone else.