While much research demonstrates that the political class in the United States has become increasingly polarized, the common claim that the larger electorate also has become more polarized has little basis. Rather, the continuing accumulation of data strongly supports the conclusion that what has occurred in the United States is the sorting of partisan sub-groups within the larger population (first identified by Alan Abramowitz and Kyle Saunders in a 1998 article
In the aggregate, today’s electorate looks surprisingly similar to that of the 1970s. Following the difficulties experienced by the Democrats between 1964 and 1972, partisanship has since fluctuated within a narrow band, as the figure just above shows. Self-identified ideology has moved within a similarly narrow band (see below). Where surveys permit the tracking of individual issues over time, the opinion distributions continue to maintain a centrist shape, and the departures tend to show leftward (toward more government services vs. lower taxes) or rightward (toward less role for government in health care and especially aid to minorities) shifts rather than a symmetric shift toward both poles. By no means has the political center vanished.
What has changed is how partisans are distributed in terms of their ideology and issue opinions. Self-identified Democrats have become more homogeneously liberal and self-identified Republicans more homogeneously conservative. And the differences between the two partisan groups on issues have increased, although not nearly as much as those among party elites. For example, ordinary Democrats and Republicans were indistinguishable on abortion until the 1990s and then began to differ (as the figure below illustrates), but even in 2012, American National Election Study data indicate that a quarter of Democrats arguably fall into the pro-life category and a third of Republicans into the pro-choice category.
Of course, none of this is to argue that sorting is unimportant. It is, and sorting contributes to the extreme partisanship we see in Washington and many of our state capitals. Compared to two decades ago Democratic candidates are more likely to be liberals than moderates, let alone conservatives, and Republicans more likely to be conservatives than moderates, let alone liberals. Moreover, Democratic candidates face the same kinds of primary constituencies whether they are running in New York or New Mexico, and the same for Republican office-holders whether running in Minnesota or Missouri. In earlier decades, they were nominated by more heterogeneous supporting constituencies.
The sorting of partisans into parties with clearer identities might result in less satisfaction for all categories of voters. According to a 2008 Comparative Study of Electoral Systems poll only about 40 percent of Americans felt that the Democratic Party represented their views “reasonably well,” about 30 percent believed the Republican Party represented their views “reasonably well,” and the other 30 percent believed neither party represented their views. We suspect that these figures would be lower today, but taken at face value, they suggest that an attempt by either party to implement its program would find a less than enthusiastic response among 60-70 percent of the public.
Can the sorting be reversed? Some analysts write as if sorting is an inexorable process, the result of demographic or economic trends that render one electoral coalition inevitably rising or ascendant. But in the argot of political science, electoral coalitions are at least in part endogenous, meaning that they not only shape what politicians do but are shaped by those politicians’ actions as well.
Strategic politicians see social and economic changes as opportunities to disrupt old coalitions and construct new ones. Sometimes we can foresee the shape of new coalitions, as when Lyndon Johnson commented that he was giving Republicans the South for a long time to come when he signed the 1964 Civil Rights Act. But in other cases the shape of future coalitions is harder to predict. In 1965 who would have foreseen that environmental protection, abortion, and other cultural issues would begin reshaping electoral coalitions by the late 1970s? While we cannot predict the shape of future electoral coalitions, we believe that the present situation is a not stable equilibrium.