WASHINGTON — Across the country this week, tens of millions of Americans have been signaling how they'll vote for president this fall.

They're doing it not by tuning in to campaign commercials, contributing to one of the candidates or registering at a polling place. Rather, they're making their political statement by attending religious services or celebrating Passover — or by ignoring the religious holidays.

The religion gap is fast becoming the country's widest political division. Those who regularly attend religious services vote Republican by a margin of 2-1, and those who don't vote Democratic by the same margin.

This growing gap helps explain why the country is so divided politically. Born in the culture wars of the 1960s — over abortion, prayer in public schools and women's rights — and deepened by competing visions of morality, it's being reinforced this year by new fights over gay marriage and the Pledge of Allegiance.

The result is a values gulf dividing the nation that will make it difficult for Republican President Bush or Democratic Sen. John Kerry to build a majority. More than that, the gap makes it hard for even a winning president to command legitimacy. Each side can barely abide the other's leaders, seeing them not only as wrong on issues but also as evil people, unworthy of governing. President Bill Clinton was loathed by one side as immoral; Bush is detested by the other as intolerant, unthinking and indifferent to the poor.

"The division is growing wider in American politics. It's almost as if the two sides live in parallel universes," said John Kenneth White, a political scientist at Catholic University in Washington and author of "The Values Divide."

"It makes it difficult to assemble a broad agenda that will break that division and allow one party or candidate to reach out across the divide," White said. The gap is widest between those who attend religious services more than once a week and those who seldom or never set foot in a house of worship.

It's narrower between those who attend weekly versus those who attend once or twice a year. And it all but disappears among those who attend once or twice a month, according to many polls.

The two major presidential campaigns approach the divide differently.

Bush is a Methodist who regularly and publicly attends church. He calls Jesus Christ the most influential philosopher in his life. He invokes his faith when making policy decisions, from limits on abortion and stem-cell research to war. Most notably, he casts the war on terrorism as a struggle between good and evil.

Kerry is a Roman Catholic who's largely kept his faith separate from his public life. "I'm not a church spokesman," he said this week. "I'm a legislator running for president. My oath is to uphold the Constitution of the United States in my public life." Our Constitution separates church and state."

The nation's cultural divide increasingly is aligned with church attendance, though with some notable exceptions: Churchgoing blacks and most Jews and Hispanics remain dependably Democratic.

As the division has grown, political strategists have taken advantage of it. Aided by groups such as the Moral Majority and the Christian Coalition, Republicans recruited churchgoing voters. Democrats grew more secular and suspicious of religion's role in public life. Working on the Michael Dukakis presidential campaign in 1988, Democratic strategist Donna Brazile felt uncomfortable talking about her faith.

New cultural forces are fueling the division. A Massachusetts court has ordered the state to allow marriage for gays and lesbians. The mayor of San Francisco defied state law to allow gay marriages there. The U.S. Supreme Court is weighing whether to remove the phrase "under God" from the Pledge of Allegiance.

At the same time, more than 50 million Americans have seen the movie "The Passion of the Christ" in four weeks, and a poll suggests that the audience could easily top 100 million. A series of books about Jesus' triumphant return to Earth to battle Satan has sold more than 60 million copies.

"The outline of politics we see today is much more cultural than economic," said a Democratic strategist who spoke on condition of anonymity for fear of upsetting the Kerry campaign. "The last time the cultural division was this clear was the 1890s."

Cultural divisions over race and Reconstruction helped keep the country divided politically through much of the 1880s and 1890s, a period like this one in that neither party could marshal a majority.

Though the religious outlook of the parties was the opposite of today's — the Republicans were secular and the Democrats led by Bible devotee William Jennings Bryan — the results were similar: States in which the majority of voters were religious voted for the religion-attuned party.

Almost every state that voted Republican in 1896 voted Democratic in 2000, and vice versa. The five exceptions included New

Hampshire, Ohio and Washington, three narrowly divided states that will be pivotal battlegrounds again in November.

Today's division reflects deeply different values.

Many of those who regularly attend religious services and vote Republican see the world in morally absolute terms and want their values universally applied. For example, if abortion is wrong, it's wrong for everyone.

"They tend to think there are absolute truths, things that are unyielding for all time," said White of Catholic University.

Those who don't regularly attend religious services, along with many liberals who do, are dependably Democrats and have a more personal view of morality. They may believe marriage should be between a man and woman, for example, but they wouldn't prohibit same-sex couples from marrying.

"They like their morality writ small," White said. "They say, 'My morality is for me, not necessarily for you.' They are not into preaching morality to others."

Can this divide be bridged?

Bush shows little interest in reaching out to nonchurchgoers on their terms. Kerry makes occasional efforts. He emerged from Catholic Mass on Ash Wednesday with his forehead smudged by ashes, and he recently cited Scripture in criticizing the president's claimed compassion for the poor and needy: "What good is it, my brothers, if a man claims to have faith but has no deeds?"

Both men face difficulties reaching too far across the divide, lest they anger their own sides. Issues such as abortion and gay marriage particularly complicate the task of building a majority coalition.

Any effort by Bush to reach toward less religious voters probably would stumble on his support for a constitutional amendment banning gay marriage. Similarly, attempts by Kerry to reach churchgoers would snag for many of them on his support of abortion rights.

Kerry faces an added challenge because he's a Catholic. Some Catholic bishops have said he shouldn't receive Communion because he supports abortion rights. As a Methodist, Bush faces no such public dissonance, though his support of the death penalty also defies Catholic teaching.

"The choice of candidates may make the division even more stark," said John Green, a political scientist at the University of Akron who's written extensively about the religion gap in voting. "I don't see how it can get smaller. It may get bigger."