Upon further research, I see he was raised Lutheran. I swear I read in an interview before that he is atheist. Maybe another former candidate, then? His ardent support of separation of church and state leads me to believe that he's not seriously religious. However, whether a practicing Lutheran or not, his stance on separation is why I would support him on that issue.
He supports gay marriage and legalization of recreational drug use, too. As a former Lutheran myself, he can't be too serious about his religion, then.