I just thought this study by the Pew Research Center was interesting. It shows the size of the major religious groups in the U.S. and their presidential preference. Note that the two largest groups -- the non-religious and white evangelicals are on opposite sides of the fence -- with the non-religious supporting Clinton and the white evangelicals supporting Trump.
The numbers are from a study done between June 15th and 26th of a random national sample of 2,245 adults, with a margin of error of 2.4 points. The margin of error for the non-religious in 5.1 points and for white evangelicals is 5.9 points. The margin of error would be higher for the other groups.
