There’s only one known instance of a church losing its tax-exempt status because it violated the Johnson Amendment, but Republicans have tried to get rid of it before.

The rule was introduced by former President Lyndon B. Johnson in 1954 when he was serving as the U.S. Senate majority leader. It banned all tax-exempt organizations like churches and charities from “directly or indirectly” participating in politics, specifically in endorsement or opposition of candidates.

Churches and other houses of worship can endorse political candidates without risking the loss of their tax-exempt status, the Internal Revenue Service said in a recent filing.