What is happening?

Richard Florida, a longtime and well-respected commentator on urban life, writes about how a few areas of the country are experiencing "superstar" prosperity, and the consequences of the fact that everywhere else is falling behind.  Unsurprisingly, superstar areas are all highly progressive.  Yet as they attract like-minded people from everywhere else to come to these few, ever-more-concentrated, areas of progressivism, the places left behind have fewer and fewer voices on the left.