MINNEAPOLIS — A minister in far northern Minnesota is testing the prohibition on political preaching.

The Rev. Gus Booth of Warroad Community Church is a delegate to this year’s Republican National Convention. He gave a sermon last month urging followers to oppose Democratic presidential hopefuls Barack Obama and Hillary Rodham Clinton.

Booth alerted Americans United for Separation of Church and State to his sermon. He advised the group, which defends church-state separation, that he’s challenging federal prohibitions on political advocacy from the pulpit.

Americans United asked the Internal Revenue Service this week to investigate whether the evangelical church, which has about 150 followers, had violated its nonprofit, tax-exempt status with Booth’s sermon.

Booth, 34, told the Star Tribune his constitutional right to free expression supersedes tax law, “and the Bible has been around longer than either.”

But the Rev. Barry W. Lynn, executive director of Americans United, said the granting of a tax exemption “is not a right, it’s a privilege” that comes with restrictions.

An IRS representative declined to comment to the newspaper June 11, saying federal law prohibits disclosing information about individual taxpayers.

Booth was picked as a GOP national delegate during the 7th Congressional District convention in April, about a month before he gave his sermon. The pastor said he originally supported former Arkansas Gov. Mike Huckabee, an ordained Baptist minister who had sought the Republican nomination, but will support the presumptive GOP nominee, Sen. John McCain of Arizona.

Booth said he hasn’t calculated what losing the church’s tax-exempt status would cost it.

“If we lost it, then so be it,” he said.

Prohibitions against leaders of tax-exempt churches preaching from the pulpit in support of a candidate have been in effect since 1954, and prohibitions against preaching in opposition to a candidate have been law since 1987.

“The IRS has seen a growth in the number and variety of allegations of such behavior by [churches and other charities] during election cycles,” the agency said. In 2004 the IRS intensified efforts to enforce tax-exempt requirements and found that religious leaders used the pulpit to endorse or oppose a candidate 12 times.

The agency said it did not recommend revoking the tax-exempt status of any of the clergy’s churches, but instead issued written warnings or assessed an excise tax.

The IRS did not identify the dozen churches.

In 2006, complaints were filed against Mac Hammond of the Living Word Christian Center in Brooklyn Park for endorsing then-candidate Michele Bachmann, now a U.S. House member, from the church’s pulpit. Hammond later acknowledged that he’d made a mistake.

“To be honest with you, with a little bit of the fallout relative to Michele Bachmann, we’re taking a little bit more careful road,” said the Rev. Brian Sullivan, the church spokesman. “I don’t think we crossed the line, but it raised concerns and suspicions.”

GOP convention spokesman Matt Burns did not respond to an e-mail message from the Associated Press in time for this story.