The exemption loss lie
At several Oregon churches the last few Sundays, worshipers have been asked to sign a petition for a state constitutional ban on same-sex marriages.

"The campaign … has raised questions about how far churches can go to promote ballot measures without jeopardizing their tax-exempt status, which carries some limits on political activity," writes James Mayer of The Oregonian. Later in the story Mayer goes into more detail:

About 1,000 churches are involved in the petition drive, said Ray Cotton, pastor of New Hope Community Church in Clackamas and an organizer of the Defense of Marriage Coalition.

Cotton said tables are set up in the church foyer and people are encouraged to sign the petitions after the service. About 1,000 people signed May 30, he said, the first serious effort to get signatures. …

[Basic Rights Oregon communications director Rebekah] Kassell said her group is monitoring the political activity of the churches working to get the initiative on the ballot.

"Talking about the issue is one thing," she said. "Actively collecting signatures, launching a political organization and gathering funds to defeat or support a ballot measure, that's something else."

The risk for churches is the loss of their federal tax-exempt status as nonprofits. … Federal laws prohibit tax-exempt churches from supporting or opposing candidates for office. … The laws do allow some lobbying on legislative matters, which include ballot measure signature drives. Lobbying cannot exceed an "insubstantial" share of the church's overall activities. The law doesn't define the term. One court said churches can devote less than 5 percent of their activities to lobbying without jeopardizing their status, though ...