Congress is polarized largely because Americans live in communities of like-minded people who elect more ideological representatives. Obama’s rhetoric about a nation of common purpose and values no longer fits this country: there really is a red America and a blue America. Polarization also has affected the two parties differently. The Republican Party has drifted much farther to the right than the Democratic Party has drifted to the left. Jacob Hacker, a professor at Yale, whose 2006 book, “Off Center,” documented this trend, told me, citing Poole and Rosenthal’s data on congressional voting records, that, since 1975, “Senate Republicans moved roughly twice as far to the right as Senate Democrats moved to the left” and “House Republicans moved roughly six times as far to the right as House Democrats moved to the left.” In other words, the story of the past few decades is asymmetric polarization.
