Everyone else is talking politics these days, and now a group of conservative pastors is challenging a tax law that says they can’t join in. But the cost for throwing in their two cents may be high — their churches could lose tax-exempt status.

Yesterday, dubbed “Pulpit Freedom Sunday,” 33 pastors aligned with the Alliance Defense Fund, a conservative legal group, sermonized about the “moral qualifications of candidates seeking office.” ADF’s website doesn’t mention Barack Obama, but not surprisingly, it sounds like the Dems’ presidential candidate did not get a lot of love.

Here’s the problem: Churches register with the IRS as 501(c)3s, a designation reserved for nonprofit, nonpartisan organizations. These types of groups get to collect tax-exempt donations, but they must abstain from supporting particular political candidates. Yesterday’s sermons were “a one-way ticket to loss of tax exemption,” according to the Rev. Barry W. Lynn, the executive director of Americans United for the Separation of Church and State. The ADF, spoiling for a legal fight over this issue, says the pastors were just exercising their First Amendment rights.

Lynn told the Center’s Buying of the President project back in March that the IRS prohibition on church politicking would eventually get to the Supreme Court. “I don’t think there’s a feeling that anybody is in a big hurry to do that because it is such a complex and controversial area,” he added. After this Sunday, the IRS will have to decide if it will take action against the offending pastors, a step that would indicate the battle is joined.

For more insight on church politicking, check out the rest of the interview with Lynn, who first got involved with the issue back when Bill Clinton was running for his first term. Lynn’s wife showed him an anti-Clinton ad in the newspaper: “Don’t vote for Bill Clinton because Bill Clinton is a sinner,” the ad read. “If you vote for a sinner, you’ll be a sinner, too.”