Large metro black churches always croosed the line
I've attended Catholic then Episcopalian churches in ATL in the 70s and 80s, heard no politics from pulpits. Sometimes I attended a couple of tent revival 'churches', again no politics. Catholic and Episcopalian ministers spoke about the esoteric life of our spirits.
After I moved to New Orleans in the late 1980s I sometimes attended 'Full Gospel' and Victory Assembly of God evangelical churches and more frequently attended the mainstream small 'Spiritualist' churches. The former were very large, mainly black congregations which did a lot of outreach in the community. Anybody who has spent time in churches with primarily black congregations know nearing elections candidates and elected politicians are as thick as flies swarming potato salad and sweet potato pies at a picnic.
A lot of organising and GOTV activities have always happened in black churches. It wasn't unusual for somebody like Congressman Bill Jefferson or Mayoral wannabe Marc Morial to say a few words from the pulpit the Sunday preceding an election. (I could describe and name many candidates -especially city council reps who campaigned from pulpits). The influential pastors frequently endorsed candidates from their pulpits. I was never comfortable with it, especially since so many of the politicos turned out to be crooks. 
Since the 19th century churches had always served as 'community centers' for black people in America. Vernon Johns, predecessor to MLKjr, preached resistance to segregation from his Dexter Ave Baptist Church pulpit in Montgomery AL. MLKjr, brought in to Dexter Ave Baptist to be a calming influence organised boycotts and other social justice activities from his pulpit.