Sean Carroll in Preposterous Universe:
People have always disagreed about politics, passionately and sometimes even violently. But in certain historical moments these disagreements were distributed without strong correlations, so that any one political party would contain a variety of views. In a representative democracy, that kind of distribution makes it easier to accomplish things. In contrast, today we see strong political polarization: members of any one party tend to line up with each other on a range of issues, and correspondingly view the other party with deep distrust. Political commentator Ezra Klein has seen this shift in action, and has studied it carefully in his new book Why We’re Polarized (out Jan. 28). We talk about the extent to which the apparent polarization is real, how we can trace its causes, and whether there’s anything we can do about it.