Here is Upshot’s writeup on “the geography of Trumpism”:
http://www.nytimes.com/2016/03/13/upshot/the-geography-of-trumpism.html?_r=0They list the variables that most strongly correlate with a county voting for Trump, and the top ones are:
1) share of the population who are whites without a high school diploma
2) share of the population reporting ancestry as “American” on the census
3) share of the population living in mobile homes
4) preponderance of “old economy” jobs (agriculture, construction, manufacturing…)