501(c)(3) organizations, including churches, are not allowed to endorse or oppose political candidates. A pastor may make an endorsement as an individual, but not as a representative of the church. IRS Rev. Rul. 2007-41 states, "Leaders cannot make partisan comments in official organization publications or at official functions of the organization."
According to AU's letter to the IRS, Booth's sermon was profiled in a local weekly newspaper, the Warroad Pioneer, under the headline, "Local pastor uses scripture to oppose presidential candidates Clinton and Obama." In addition, the Minneapolis Star Tribune reported that Booth said during his sermon, "If you are a Christian, you cannot support a candidate like Barack Obama or Hillary Clinton for president because he/she stands opposite of every one of the Biblical mandates we have addressed today."
AU said the message Booth sent them said, "I am writing you to let you know that I preached a sermon in my church on Sunday, May 18, 2008, that specifically addressed the current candidates for President in the light of the Bible. As you can see from the attached newspaper article, I specifically made recommendations as to who a Christian should vote for."
ABC News said Booth invited an IRS investigation. "Booth, 34, is one of several religious leaders who this year hope to challenge federal law by flouting the regulations about endorsing candidates from the pulpit — a move that could potentially cost them their tax-exempt status, creating financial ruin for many congregations." Booth told ABC News, "The government is trying to censor me and other religious leaders. I may be taking on the IRS, but the IRS has taken on the Constitution unchallenged since 1954. I feel like the only law that should dictate what I am allowed to say is the First Amendment."
Privacy laws prohibit the IRS from announcing its investigations, so it is currently unknown whether the agency has opened an investigation into this case. However, it is likely that Booth will make a public announcement if the IRS starts an investigation, considering he wrote a letter to the IRS explaining what he had said, challenging the agency to do something.