What is remarkable is how distinct the cultures are between Belmont and Fishtown, how unequal they are, and how much further apart they have grown in the five decades from 1960 to 2010. Not only their income levels, but their participation in crime, their attitudes toward marriage and single parenthood, their work habits and economic values, and their participation in religious traditions (Belmonters are much more likely to practice faith). But it goes further than this. The cultural differences “have to do with the food the Belmonters eat, their drinking habits, the ages at which they marry and have children, the books they read (and their number), the television shows and movies they watch (and the hours spent on them), the humor they enjoy, the way they take care of their bodies, the way they decorate their homes, their leisure activities, they work environments and child-raising practices.”

At the risk of oversimplification, I think it’s a fair generalization: Romney is brilliant in Belmont. But he flounders in Fishtown.

As it happens, Mitt Romney’s primary residence was in the real Belmont until very recently. He’s lived most of his life in “Belmont.” He has lived and moved amongst the upper crust, in a culture that seems further and further alienated from Fishtown all the time. Belmont Republicans love him. He shares their values, possesses the virtues they extol, excels at the things they admire. They understand him and they trust him.

Fishtown Republicans do not. Fishtown Republicans have increasingly insisted on identity politics — having candidates they can identify with, candidates they might expect to find drinking beer at their neighborhood barbecue — because they find so many politicians are increasingly distant from them.