The Weekly Standard's Joseph Bottum has written an interesting essay on the moral and doctrinal incoherence of John Kerry's Catholicism.
Usually, the personal religious issue has only cropped up among the anti-Bush Left, which condescendingly and even intolerantly belittles the President for his own spiritual convictions, while ignoring Kerry's, such as they are. But Bottum makes a pretty good case for Kerry being, at best, a half-assed Catholic, and it may be that the conservative interest in exploiting Kerry's unconvincing, Dean-like grasp of matters ecclesiastical has yet to be fully realized.
There's little doubt that Kerry's already got the atheist/agnostic vote wrapped up, but he'll probably also pull in the fundamentalist Muslim vote without even having to get down on his knees and face Mecca.