Church attendance is a strong predictor of how high-income people vote, not such a good predictor for low-income voters.
There’s lots of talk about religion and income and voting, but people don’t always know that interactions are important.
Here are some time trends (from this paper with David Park). The graphs below show the difference in Republican vote between rich and poor, religious and non-religious, and their interaction (that is, the difference in differences), computed separately for each presidential election year:
As others have noted (although not, as far as I know, looking at interactions), it all started in 1992. We heard a lot about the Moral Majority back in 1980, but it doesn’t seem to have started showing up in voting patterns until Clinton.
You can read more about interactions in the linked article. The key points are that (a) higher-income voters support the Republicans and have done so for awhile; (b) more recently, churchgoers have supported the Republicans, (c) the difference between churchgoers and non-churchgoers is much greater for the rich than the poor.