The agency has long had the authority to revoke the tax-exempt status of religious and charitable groups  known as 501(c)(3) organizations under a law passed in 1954  if they participate in “activities that favor or oppose one or more candidates for public office.”

Typically, it does not initiate investigations but acts on complaints from individuals or groups like Americans United, which filed the complaint against Mr. Manning. Investigations can take years, in part because of the process of deposition-taking and verification, and in part, experts say, because of a sensitivity to the special role of religious freedom in the country’s history. Only a handful of churches have ever lost their tax exemptions, and then only temporarily.

It is unclear whether the accessibility of evidence on the Internet will produce more or speedier investigations. So far this year, the rate of new cases the revenue agency has pursued roughly matches that in the campaign years of 2004 and 2006  when there were about 100 annually, according to Nancy Mathis, an agency spokeswoman.

But even though many churches and charity groups have had Web sites for years, the agency issued its first guidelines on the matter in June 2007. In a memo to enforcement officers posted on its Web site, which many tax-exempt groups monitor, the I.R.S. said that if “a 501 (c) (3) organization posts something on its Web site that favors or opposes a candidate for public office, the organization will be treated the same as if it distributed printed material, oral statements or broadcasts that favored or opposed a candidate.” Several clarifying guidelines were issued last month.

Since the early 1990s, when the revenue service imposed severe penalties in several high-profile cases, including a two-year revocation of the tax exemption for Jerry Falwell’s “Old Time Gospel Hour,” most religious organizations and clergy members have been careful to keep within the I.R.S. limits.

To explain the latest changes, many religious groups have held online seminars, or Webinars. The liberal-leaning Interfaith Alliance, which favors strict enforcement of the rules on the principle that religion is compromised by involvement in partisan politics, has arranged conference calls for clergy members to discuss the new guidelines with I.R.S. officials.

Ms. Mathis, the agency’s spokeswoman, declined to discuss its investigative techniques, but said that cases springing from Web sites had raised new issues. If a cleric appears on his or her church’s Web page endorsing or attacking a candidate, she said, that is clearly no different from a sermon in the pulpit.