This year's presidential campaign has proved to be one infused with religion, with President Bush's reelection bid buoyed by evangelical Protestants and Democratic challenger John F. Kerry under fire by some of his fellow Roman Catholics for his stance on abortion rights.

But the issue of religion and politics reaches beyond the candidates. Some forms of political involvement can endanger a church's tax-exempt status, and religious leaders report that they and their congregations increasingly are being scrutinized for any action that might violate that rule, including what is said in sermons.

"It's a concern thrust upon us by the administration and by polarized political perspectives," said the Rev. Graylan S. Hagler, senior pastor of Plymouth Congregational United Church of Christ in Northeast Washington. "We have become polarized as a country, with the right wing scrutinizing the liberals and progressives and the liberals scrutinizing the conservatives. And each is willing to call 'foul.' "

Since March, when a church in Austin allowed the Republican Party to hold a fundraiser in its sanctuary, Americans United for the Separation of Church and State has filed complaints with the Internal Revenue Service against seven houses of worship, charging them with failing to observe the limits on political activity by a tax-exempt, nonprofit religious organization. Two of those complaints involved clergy endorsing candidates from the pulpit, with one minister backing Kerry and the other supporting Bush.

In April, the pastor of Charles Street AME Church in Boston introduced visiting candidate Kerry as "the next president of the United States." In July, the pastor of First Baptist Church in Springdale, Ark., told worshipers to "vote God" in November, contrasting the candidates' position on abortion and other issues. He did not mention the candidates' names but displayed images of each one behind him as he spoke favorably about Bush's policies.

"There's a bright line drawn by the IRS and tax law," said Joseph L. Conn, a spokesman for the Washington-based Americans United. Clergy "can talk about issues in an unlimited way, but they cannot urge people to vote for or against a candidate."

The Becket Fund for Religious Liberty, a legal support group for religious organizations in Washington, considers the threat of tax-exempt revocation to be unconstitutional if it infringes on the right of clergy to speak freely.

"While the Supreme Court has upheld tax penalties for nonreligious charities' political activity, we believe there is a difference of constitutional significance when religious ministers speak from the pulpit to their own congregations," Becket Fund Chairman Kevin J. Hasson wrote in a Sept. 17 letter sent to 300,000 houses of worship across the country. "We encourage you to contact us immediately if the IRS threatens your institution's tax-exempt status for anything you say from the pulpit. . . . We will defend free of charge any good faith religious message -- left, right, or center, wisdom or nonsense -- preached from the pulpit."

Several houses of worship have been in communication with the Becket Fund about complaints they say have been filed with the IRS against them, said Jared N. Leland, media and legal counsel for the fund.

A spokeswoman for the IRS said she could not comment on the existence or status of any investigation. She referred to the "Tax Guide for Churches and Religious Organizations," a 28-page document on the IRS Web site (No. 1828) that offers guidance on what actions are allowed under federal tax law.

Religious leaders, as individuals, may declare support for candidates or parties but "cannot make partisan comments in official organization publications or at official church functions," according to the guide.

For example, ministers who endorse a candidate at a news conference outside the church or allow their names to be included in a newspaper ad paid for by the candidate do not violate the prohibition against "campaign intervention," the guide says. But a minister cannot endorse a candidate during a worship service or in a newsletter, even if the minister does so in a column called "My View" and pays for that portion of the newsletter, according to the guide.

Local clergy interviewed for this article generally had little knowledge of tax laws involving the political activities of houses of worship.

All said they have not endorsed a candidate by name from the pulpit, and would not. Yet each said that pastors, rabbis, imams and other spiritual leaders have the right to speak freely during worship as long as they do not preach hate or incite violence.

"One of my highest ministerial values is the freedom of the pulpit," said the Rev. Dean J. Snyder, senior minister of Foundry United Methodist Church in Northwest Washington. "If a person feels called upon to endorse a candidate as part of their proclamation, I defend them to the hilt. As far as I'm concerned, lawyers or the IRS don't dictate what's said in the pulpit."

The Rev. Martyn Minns, rector of Truro Episcopal Church in Fairfax, said he never has endorsed a candidate in a sermon or even announced his personal preference. "I haven't done that, can't imagine doing that."

On the other hand, "I can't say I'd never do that," he said. "There might be a truly bad person running for office, someone who advocates racist policies or other things contrary to Scripture."

Such a situation arose for Rabbi Barry Freundel of Kesher Israel synagogue in Northwest, when he served a synagogue years ago in Connecticut. The town's mayor, who was running for reelection, had made anti-Semitic comments in public and even wrote an offensive letter on the occasion of the synagogue's 75th anniversary.

"I didn't mention him by name," Freundel said. "I said, 'This is an important election coming up. Keep in mind the record of the two candidates.' "

Despite their support for a free pulpit, those interviewed said endorsements, direct or indirect, are unwise.

One of greatest risks is dividing the congregation over politics, endangering its religious mission, several said. This is especially true in the nation's capital, where every congregation is likely to have some members who are Republican, Democrat or independent, or hold political jobs.

"This congregation does not need me to tell them how to vote," said Foundry's Snyder. "But they do need me to provide a biblical and theological perspective of faith on important issues and on how we live together as a people."

Yusuf Saleem, imam of Masjid Muhammad in Northwest Washington, said his messages at Friday prayers -- the weekly communal worship for Muslims -- focus on the "glorification of God" and on being good citizens of one's neighborhood, city and country. His mosque reserves political discussions for bipartisan forums where candidates or their representatives appear, he said.

Saleem has an answer for anyone who wants to know how he stands on a political race. "This is how the American system works," he tells them. "When you go into the booth, it's a private booth, a private vote, and that's how to keep it."

M. Bruce Lustig, senior rabbi of Washington Hebrew Congregation, also in Northwest, said "any sermon worth its salt" will address societal problems with overt or suggested connections to political issues, such as gun control and welfare. But he would never tell his congregation of more than 3,300 families how to vote -- "that's 10,000 some-odd people of all predilections," he said.

"I can tell them what Judaism teaches," the rabbi said. As to which candidate or party he believes will do the best job, they can "extrapolate" if they choose to do so, he said.

Plymouth Congregation's Hagler said it's important to speak out against government policies that don't follow such New Testament imperatives as acting peacefully rather than vengefully and helping the disadvantaged.

"I hope I've prayed and preached the Gospel well enough so that the congregation comes to the same conclusion" as he does about a political race, Hagler said. "But people have to make their own decisions."

Revocation of tax-exempt status is rare. The best-known case involved a church in Vestal, N.Y., that worked against Bill Clinton in the 1992 presidential campaign and purchased full-page ads in USA Today and the Washington Times headlined "Christians Beware." The IRS revoked the church's tax-exempt status, and federal courts upheld the decision.