This cartoon from The Seattle Times illustrates how America's economic pizza is actually sliced per capita, highlighting the massive disparity between the Top 1%, the merely wealthy, the upper middle class, and the lower 50%.
In my experience the difference in voting is really between the educated class and the uneducated class. Educated people are tend to be left wing. Uneducated people tend to be right wing. I'm pretty sure the data bears that out.