Here’s an interesting piece from Think Progress analyzing Trump’s following among Evangelicals. Apparently he has been attracting a particular subset of the Evangelical community in particular, people who identify as Evangelical, but are not particularly observant.
For example, only 38% of Trump’s followers report attending church on a weekly basis compared with 56% of social conservative voters.
This may well explain why Trump’s religious gaffes do not seem to be shaking his supporters much. They are not going to judge Trump harshly for paying lip service to being a Presbyterian when they themselves are not particularly observant.