The Alliance Defense Fund, a far-right Christian legal organization, is agitating to allow preachers to endorse candidates from the pulpit. Yesterday, 33 pastors in churches across the country participated in ADF’s "Pulpit Freedom Sunday" campaign by delivering political sermons and essentially daring civil society to do anything about it.
The issue is the tax code, not the First Amendment.
Currently, pastors can talk about political issues as much as they want, but they can lose their tax-exempt status if they instruct their parishoners to vote for, or against, a specific candidate. The ADF wants taxpayers to subsidize electioneering by churches. Pastors are currently free to endorse candidates as private individuals, they just can use their churches to stump for a candidate if they want to stay tax-exempt.