There seemed to be two major reasons for this tribalism. When people did have occasion to change location, they often had a choice of nearby regions and picked the one in which they felt most comfortable—the one in which the people were most like themselves. If a new job was to be filled in Denver, for example, a Republican-leaner might tend to live outside of town and commute in; a Democrat-leaner would more likely head for the heart of town. There is also a group dynamic taking place. Those who vote Democratic or Republican don’t just represent different political philosophies; they represent cultures with different lifestyles and different worldviews. People who migrate into a culture tend to assimilate into that culture. There will be subtle but definite pressures in urban areas, for example, to think and vote like the majority
I was quite interested in learning how this process has proceeded since the last election in 2008. I haven’t found data accumulated in exactly the form presented by Bishop, but Mark Newman of the University of Michigan has posted data that is perhaps even more informative. Newman provides this chart of the winning party in each county. Red is Romney/Republican and blue is Obama/Democrat.
Newman also provides a chart in which the color of the county varies between red and blue according to a scale in which a Republican vote of 70% or more is pure red, and a Democratic vote of 70% or more is pure blue.
Clearly, in the regions where one party dominates, there are significant areas in which the vote is reaching the 70% saturation point. That is rather incredible.
Where does this end? There was a report that there were a number of precincts in an Ohio city in which Romney received not a single vote. Undiluted partisanship will breed more intense partisanship. Who would want to be the last Democrat in a Republican precinct?
Perhaps demographics will come to our rescue and define one party/culture to be dominant and temper this polarization, or realign us so that we fight over different issues. Something better come to our rescue—and quickly.