Meanwhile, says Barton, a pastor can talk about any issue he wants to. If he wants to preach against same-sex marriage or abortion, he can. And he can talk about the voting records of individuals or groups on those matters.

Of course, how a minister describes the issues is what makes the situation tricky. "It's very clear in the party platforms that one party does support traditional marriage and opposes abortion and supports school prayer--and the other opposes that," Barton says. And that makes Republican candidates the obvious choices. "This is your logical home if you're concerned about Biblical issues," Barton says.

In a 1996 critique of Barton's documentary, "America's Godly Heritage," the Baptist Joint Committee on Public Affairs said of Barton: "His presentation has just enough ring of truth to make him credible to many people. It is, however, laced with exaggerations, half-truths, and misstatements of fact."

Barton has said that God influenced his sense of mission. In America: To Pray Or Not To Pray? Barton writes: "In July 1987, God impressed me to do two things. First, I was to search the library and find the date that prayer had been prohibited in public schools. Second, I was to obtain a record of national SAT scores (the academic test given to prospective college-bound high school students) spanning several decades. I didn't know why, but I somehow knew that these two pieces of information would be very important."

As a result, Barton writes that he learned America has declined because of the 1962 and '63 Supreme Court rulings banning school-sponsored prayer. He believes God is angry at the country and has retaliated.

Barton expounds on these views--in somewhat more opaque terms--on the Wallbuilders website. He doesn't specifically call the United States a "Christian nation," but he also doesn't say that it isn't. A typical explanation: "We have received numerous questions from people who have been misled by the claims that are being made, namely, that America was not founded as a Christian nation."

Rob Boston, an official from Americans United for Separation of Church and State called Barton's advice to pastors that they can endorse from the pulpit "inaccurate, misguided, and dangerous. The IRS has never said that. It's also important for religious leaders to remember that Barton is a partisan operative. He doesn't care if a few churches fall prey to the IRS along the way."

In the Beliefnet interview, Barton was heavily critical of Americans United for trying to "intimidate" conservative Christian ministers. But Boston said his organization has also reported three black churches to the IRS since August for endorsing Sen. John Kerry from the pulpit.

"A pox on both their houses," Boston said. "Both parties are trying to politicize houses of worship."