Catholic bishops have increasingly criticized Kerry's pro-choice stance on abortion and other matters such as priestly marriage and stem-cell research. And the bishops have formed a task force to consider how to deal with politicians in church ranks.

"It would be a dilemma for any politician in any religion," said Mary Carter Waren, professor of religious studies at St. Thomas University in Miami. "It's just that the Catholic Church is an easier target, because we're so organized."

Kerry took Holy Communion on Sunday at the Paulist Center in his hometown of Boston, raising tensions another notch with American bishops. Some have ...