Presidential candidates appeal to the "working class" and "ordinary people" with the promise of unifying America for the "common good." But that turns out to mean different things in different places, and it's not just a matter of Red States versus Blue. Wealth and mobility have freed Americans to move wherever they want to and they end up with people just like themselves, culturally as well as politically. What might sound obvious turns out to be an index of major change over the past 30 years. Is segregation-by-lifestyle dividing cities and neighborhoods? Whatever happened to "class?" Is political unification possible any more?