According to a poll from the Pew Research Center, 18% of Americans believe that Obama is a Muslim, up from 11% a few months ago. One reason people doubt is because important religious leaders like to sow doubt. Like this asshole:
This being "born a Muslim" nonsense is foolishness. No one is born any religion. Babies are born stupid and ignorant, without the ability to believe anything. Religion is indoctrinated into young children, usually by their parents. It is not genetic like race, sexual orientation, or hair color. The idea that one can be born Jewish, Muslim or any other religion is pure propaganda.
And, this Graham prick knows this. He's just trying to cast doubt on Obama's Christianity with the subtle "I have no reason to doubt him, so I'll believe him" line. Graham is purposefully playing to the bigots who fear Islam, by trying to cast doubt on Obama, without actually accusing Obama of anything. And, Graham gets away with his pricknacious assholery because CNN does not immediately challenge him.