Economic research shows that people who feel they are becoming better off over time are more generous, altruistic and participatory. No wonder, then, that the Great Recession and limp recovery of the past three years have given us something as pinched and polarizing as Tea Party politics. The debt-reduction deal that was cut after many weeks of partisan wrangling may have temporarily saved the U.S. from default. But it has exacerbated the real problem underlying our woes: the fact that most people not only feel but actually are much worse off than they were three years ago.
While the income share...