Was just talking with a friend about this -- we agreed that if this were an American businessman getting the blessing and will of the Christian God from a priest or a bishop, we probably wouldn't think too much of it.

A lot of people in the US are uncomfortable and many people are alarmed when a political candidate says god wants them to win, Christian or not.

The whole "freedom of religion" thing over here is supposed to keep such nonscientific thinking allowable, but outward religious affiliation (or endorsement) for political actors usually only strengthens the part of the fanbase that condones such thinking. This is usually a significant portion for "conservative" actors who tend to pander to that same set of moral sensibilities and nonscientific rhetoric, since it keeps them popular amongst that portion of their constituency (e.g. any religious statement Cruz or Trump ever made)

However, generally a lack of vocal endorsement of a particular religion is seen as a plus for candidates since it's not directly controversial, except for with religious voters who can't possibly fathom how someone could disagree with them on the topic.