St. Louis' new Archbishop Raymond Leo Burke addressed Kerry's liberal views shortly before the Missouri primary. "I would have to admonish him not to present himself for Communion," Burke said on a local TV news show. Kerry's hometown archbishop, Sean O'Malley of Boston, has in the past given Kerry Communion but recently said, "These politicians should know that if they're not voting correctly on these life issues that they shouldn't dare come to communion."
The more political and therefore bigger threat for Kerry is if a public spat with the bishops made him seem lacking in conviction or genuine faith. Will he come off as someone who calls himself Catholic but doesn't act like one? Or will he just seem like many other American Catholics, defining his faith in a genuine and earnest way—just not the way the church itself does?
Politically speaking, what's his best approach? He could agree not to take communion, a confession of the "defective" nature of his faith, but a sign also that he's willing to play by the rules of the church and at the same time stick by his political scruples. But he would thereby insult, in effect, all other pro-choice Catholics who take communion on principle. He could attack the church's position, thrill liberal Catholics, and look like a man of honor. But that could spook moderate Catholics.
His best tack is probably to talk proactively about how his Catholic faith has affected other parts of his life, like his commitment to helping the poor, for example. It would show that he's a religious man who takes the Catholic faith seriously, even though he defines it in his own way like many American Catholics do. George Bush is already running ads asserting that he's a man of principle, a notion that seems plausible in part because of his widely publicized faith. Weirdly, the fact that after Kerry's first marriage broke up, he sought an annulment might show some Catholics that he cared enough about the rules of the church to go through the process—though it also gives an excuse for critics to probe the circumstances of the divorce and annulment.
As far as the election goes, it's less important for Kerry to agree with the church's positions than it is that he be viewed as a person with strong religious convictions. Obviously having a Catholic-style marital flameout is probably not sufficient. He'll have to offer something a bit more Dororthy Day and a bit less Ted Kennedy. The more he rebuffs the church's theology, the more he'll have to highlight what makes him truly pious.