Few are swayed by a candidate's pro-choice policy. "Will Catholics vote against Gov. Carter, Mr. Mayor, because of his abortion stand?" The mayor of Chicago stared at the reporter with the bemused frown he reserved for silly questions. "They don't vote that way." Twenty-eight years later, they still don't vote that way. Nevertheless, in the run-up to the last seven presidential elections, experts on both sides have predicted that the "Catholic anti-abortion" vote would cause trouble for the Democrats, especially given the drift of Catholics from Democratic alignment. Both these "theories" — a Catholic anti-abortion vote and a Catholic realignment...