The last time a major party nominated a Catholic for president, in 1960, John F. Kennedy had to defend his independence. "I believe," he told a gathering of Protestant ministers, "in an America where the separation of church and state is absolute, where no Catholic cleric would tell the president, should he be Catholic, how to act, and no Protestant minister would tell his parishioners how to vote."

It worked. According to the Gallup organization, the Democratic share of the Protestant presidential vote in 1960 was 38 percent--almost precisely what it had been four years earlier (37 percent), when there was no Catholic on the Democratic ticket. Among Catholics, the Democratic vote surged from just over 50 percent in 1956 to nearly 80 percent in 1960. In other words, there was evidence of Catholic pride, but not of anti-Catholic prejudice.

This year, Democrats are nominating another Catholic. But the problem John Kerry faces is different from Kennedy's: It's not potential bigotry from non-Catholics; it's pressure from the Catholic Church. Kerry supports abortion rights. "There is no overturning of Roe v. Wade," the senator from Massachusetts said at a NARAL Pro-Choice America rally last year. "There is no packing of the courts with judges who will be hostile to choice."

That view, of course, is incompatible with Catholic teachings. But then, the views of many American Catholics are incompatible with their church's teachings. The Catholic Church opposes the death penalty. But the vast majority of American Catholics, like the vast majority of Protestants, finds capital punishment for murder acceptable (74 percent of Catholics and 72 percent of Protestants in a May Gallup Poll).

The Catholic Church opposes gay marriage, but Catholics are more favorable to it (43 percent) than are Protestants (28 percent). Catholic bishops have criticized the war in Iraq, but even more Catholics than Protestants think that the war was worthwhile (56 percent of Catholics; 51 percent of Protestants).

Abortion is an issue on which the Catholic Church allows no deviation from its teaching. According to a statement last week by the U.S. Conference of Catholic Bishops, "It is the teaching of the Catholic Church . . . that the killing of an unborn child is always intrinsically evil and can never be justified." Nevertheless, Gallup finds more Catholics than Protestants holding the opinion that abortion is acceptable in all or most circumstances.

In their statement on "Catholics in Political Life," the U.S. bishops denounced Catholic politicians who support abortion rights as "cooperators in evil" and urged them to "examine their consciences as to their worthiness" to receive communion. The statement allows bishops to make their own judgments about whether to deny communion to such political figures.

This year, Kerry echoed Kennedy's words, but he had a different target in mind. "I am not a spokesman for the [Catholic] Church," Kerry said, "and the church is not a spokesman for the United States of America." But the Catholic Church, predictably, had a retort. In a direct contradiction of Kennedy's 1960 remarks, the bishops said, "The separation of church and state does not require a division between belief and public action . . . but protects the rights of believers and religious groups to practice their faith and act on their values in public life." That echoes the view of the Religious Right--that the principle of separation prohibits the state from interfering with religion, not vice versa.

This year, unlike 1960, the Catholic vote looks like a swing vote. A Time poll shows Catholic voters split, 45 percent for Kerry and 43 percent for President Bush. What's changed since 1960 is the emergence of a social agenda that includes issues--such as abortion and gay marriage--on which the Catholic Church has doctrinal positions. Those issues have given Republicans an inroad with Catholic voters.

When Bush went to Rome this month to meet with the pope, he asked the Vatican to encourage U.S. bishops to speak out more about those issues. Bush is calculating that if he can get the Catholic Church to be more forceful in promoting its own agenda, that would advance his agenda. Deal Hudson, a conservative Catholic leader and the publisher of Crisis magazine, said, "This is the moral and social agenda of the Catholic Church that the president agrees with the church on and is seeking to support and actualize in this country."

In other words, Bush is doing what the bishops are exhorting Catholic politicians to do. The problem is, most Catholics don't like to see their church get involved in politics. In the Time poll, about 7 in 10 Catholics said their church should not try to influence the positions of Catholic politicians or how Catholics vote.

That's not the issue, conservatives argue. In Hudson's view, the poll findings suggest "that the bishops should keep from getting involved in partisan politics." Bush didn't ask the Catholic Church to endorse him. He asked the Catholic Church to speak out more forcefully on certain issues. Still, it is highly unusual for a politician to make such a request of religious leaders. And Kerry called Bush's request "entirely and extraordinarily inappropriate."

The Bush-versus-Kerry battle for the Catholic vote is, in some respects, a battle between observant and dissenting Catholics. Those two constituencies disagree, not only on the teachings of their church, but also on how aggressively it should try to advance its political agenda.

William Schneider is a resident fellow at AEI.