For these maps, I found the percentage of each state’s total population voting for each candidate in all presidential elections from 1972 to 2016. The candidate who had the highest percentage (in any election year) is the “winner.”
I realize that it would be more ideal to use the actual eligible voting population, rather than the total population, but I have been unable to find that data further back than 2000. So, for the sake of uniformity, I have gone with total population. I do not believe that this greatly affects the results, at least not in the 1972-2016 time frame.