Regionalism

Politico has a demographics-driven article entitled "These Disunited States." It focuses on the extent to which various regions hold different views, and the degree to which those views have been stable over time.

People moving from a liberal area to a conservative one and vice versa tend to have political attitudes that resemble those in their destination, not their old home.

For decades now, relocating Americans have chosen to move to communities where people share their values and world views.

The proportion of voters living in counties that consistently give landslides—more than a 20 percent margin of victory—to one party or another increased from 26.8 percent in 1976 to 48.3 percent in 2004. The volume of people is significant, and has benefited the GOP, with a net 13 million people moving from Democratic to Republican landslide counties between 1990 and 2006 alone.

Birds of a feather do, in fact, flock together. In a mobile society, people with similar beliefs tend to do the same.