One of the subterranean issues in the presidential contest is the Democratic candidate’s status as a member of the Roman Catholic Church. He’s the first Catholic nominee since another Massachusetts Democrat with the same initials, and that is a potential problem for a Republican Party that’s been working overtime to turn Catholics into a GOP constituency group.
Today’s New York Times has a big writeup about one aspect of the Republican strategy to blunt or even invert the electoral impact of Kerry’s Catholicism: the campaign by a handful of conservative Bishops to convince Catholics they have a religious duty to reject their co-religionist because of his positions on abortion and stem-cell research, and his rejection of a constitutional amendment banning gay marriage. There’s a lot of evidence that it’s not exactly the right moment for elements of the American hierarchy to get too high and mighty about lecturing the laity on their moral obligations, but that won’t stop them from trying.
Aside from the effort to convince voters that Kerry’s a bad Catholic, there’s a slightly subtler BC04 argument that he’s not much of a Catholic at all, being a “liberal” and a “moral relativist” and a “flip-flopper,” etc., in comparison with the resolute Christian in the White House (never mind that Kerry seems to go to church a lot more often than Bush).
Kerry himself has followed the quaint custom (more common among American Catholics than evangelical Protestants) of trying to keep his religion out of the campaign; as he put it in his acceptance speech in Boston, he doesn’t wear his faith on his sleeve.
But for the record, here’s what Kerry said about the political implications of his faith in his 2003 book, A Call to Service:

I am a believing and practicing Catholic, married to another believing and practicing Catholic. And being an American Catholic at this particular moment in history has three particular implications for my own point of view as a candidate for the presidency.
The first two follow directly from the two great commandments set for in the Scriptures: our obligation to love God with all our hearts, souls, and minds and to love our neighbors as ourselves. The first commandment means we must believe there are absolute standards of right and wrong. They may not always be that clear, but they exist, and we must honor them as best we can.
The second commandment means that our commitment to equal rights and social justice, here and around the world, is not simply a matter of political fashion or economic and social theory but a direct commandment from God. From this perspective “Christian” bigotry and intolerance are nothing less than a direct affront to God’s law and a rejection of God’s love.
There’s a third facet of being an American Catholic that I take very seriously. We’ve always been a minority in this country, and have sometimes suffered persecution. To a larger extent than Catholics elsewhere, we have supported and relied upon the constitutional principle of separation of church and state to guarantee our right to worship and our liberty of conscience. That tradition, strongly advanced by John Kennedy in his quest to become our first Catholic president, helped make religious affiliation a nonissue in American politics. It should stay that way.