People believe that a person religious affiliation will affect his decision making. This is why most people are obsessed with the president's religious affiliation and several other leaders who have a lot of influence in policy formulation.
You're right, it should have nothing to do with running a nation. There is such a huge majority of christians in our country that no politician would be elected if he/she weren't christian. I think it's because many christians believe that if you're not with them, you must be against them. Many of them have this overwhelming need to be right all the time, even when they're wrong.
On one hand he shows his inclination towards religion and on the other hand he vouch for GAY OR SAME SEX MARRIAGES. Beware they are all stereotyped personalities they are not normal man THEY ARE POLITICIANS.
I do not believe religious affiliation should be nearly as important as having someone who lives by a consistent set of moral and ethical principals. Walking into a Church makes you no more a Christian than walking into McDonalds makes one a BigMac.