What difference does it make if a candidate is viewed as a person of faith? I don't think the key is the purity or coherence of his religious practice. New York Times columnist David Brooks (who's still my favorite conservative) nailed it precisely when he said of his fellow countrymen, "Their President doesn't have to be a saint, but he does have to be a pilgrim. He does have to be engaged, as they are, in a personal voyage toward God."
This is true for three reasons, none of which have to do with God. First, if Kerry's uncomfortable with religion then he's uncomfortable with Americans. Media managers love having him photographed riding a motorcycle because it shows he can connect with regular folks, who apparently all ride motorcycles, too. If Kerry's really secular, he's abnormal.
Second, the fact that people view Bush as a man of faith is very much connected to their viewing him as decisive and steadfast, two of his strongest assets. A man of faith is a man of conviction, and vice versa. So, Kerry's unwillingness to talk about his faith feeds into one of his great weaknesses, his reputation as a waffler.
Finally, he needs to talk about his faith because it would strengthen him on the most important issue of the campaign—terrorism. Let's face it: It really doesn't matter if a president has strong inner spiritual reserves if the focus of his presidency is changing the capital-gains rate.
But when the country is at war, people appropriately look for signs that the president has real strength. Americans believe that one of the most important sources of inner strength is faith. During the darkest hours of the country, when the president is wandering the halls alone, will he find himself talking to God or to the oil paintings of past presidents? Putting aside the question of whether, in either case, someone is talking back, voters are going to be more comfortable with the commander in chief who has serious resources, and I don't mean financial ones.