Truly if a President takes his Oath Of Office seriosuly, relgion shouldn't be a consideration. His oath is to uphold the constitution of the United States and defend America. That's it.
That being said, there are waaaay too many religious groups who seek to elect a candidate based on religios beleifs. Personally, I don't give a crap what religion the President is, just as long as he doesn't expect me to adhere to his beliefs like they were the law of the land. Here in the South, too many relgious groups control things that they should not have a hand in. For instance, rules regarding the availability of alcohol, rules regarding acceptable sexual conduct between people (even if they're married), etc.
Personally, if we had a Jewish president the only thing I'd want to know is where does he get his bagels so I can get some too!