I am collaborating on a research paper where one of our variables is political affiliation across the United States. I will be creating a series of historical maps. I'm looking for the percentage of the population that is Republican, Democrat, and Independent in each zip code in the US. If zip code isn't available, county would work too, or statewide if nothing else. I've searched online and have only found 2008 and 2012 election data.
Does anyone know where I could find this historical political affiliation data? I need data from 1980 to present day.