Partisan Polarization in the US Electorate

Abstract

The literature on party polarization in American politics focuses on two distinct (though related) topics, elite polarization and mass polarization. The literature began at the elite level, focusing on the divisions between the parties as captured in roll-call voting behavior in Congress (though there is a small literature looking at elite institutions beyond Congress). At the elite level, there is little debate: elites have become more divided since midcentury, and today are as polarized as they have been in living memory (though levels of polarization in the 19th century were higher). The debate at the elite level centers primarily on the causes of this polarization, with five related main arguments: changing party strategies, redistricting, primary elections, activists, and changes in the mass public. With the exception of redistricting, which finds only very limited empirical support in the literature, there is solid evidence supporting each of the other explanations. Determining the relative importance and contribution of each factor, however, is somewhat more complicated and remains an open question. While it is clear that elites are polarized, the state of affairs for the mass public is somewhat muddier. After the disputed 2000 election, electoral polarization became the conventional wisdom. While some scholars agree with this popular consensus, others do not, and argue that Americans have not become more divided over the past generation. What is clearer, on the other hand, is that the mass public has become better sorted—citizens have aligned their partisanship and ideology so that Democrats are more likely to be liberals and Republicans are more likely to be conservatives. Elite polarization drove this party sorting: as elites polarized, they clarified where the parties stood on the issues, which made it easier for citizens to align their party and issue positions. Another portion of the literature also addresses the consequences of these mass and elite changes. Scholars are essentially unanimous that polarization harms the policy process by fostering gridlock, leading to suboptimal policy outcomes. There is more debate, however, about whether polarization (at either the mass or elite level) harms the electoral process. While some argue that it leads to a harmful disconnect between voters and elites, others claim it allows voters a clearer choice between the parties, which boosts participation. It is also worth mentioning that various authors operationalize the concept of “polarization” differently. Some authors conceptualize polarization as a static construct: are Democrats and Republicans polarized (that is, divided) at a particular point in time? Others refer to polarization over time: have Democrats and Republicans become more divided over a period of years? In each work, readers should pay close attention to determine exactly how the author is using “polarization” in a particular work.