In discussions about the causes and effects of American political polarization, the idea of “sorting,” an increasing correlation over time between characteristics in a group, is likely to play a primary role. In the context of polarization, these characteristics are associated with politics; for example, more Democrats are identifying as liberals over time (and vice versa), and more political party members are relocating to the same places as other party members over time.
Political scientists debate whether polarization is happening at all, or whether it consists entirely of partisan-ideological sorting within both groups of elected officials and the mass electorate . This argument highlights the difference between issue distance, the ideological distance of mean issue positions between political groups, and issue consistency, the variation of issue positions within groups. If there is very little variation in the positions held by group members, that group is considered highly sorted.
Over the last several decades, issue distance between Democrats and Republicans- the two largest political groups- has increased relatively little, while issue consistency in both these groups has increased substantially . Consistency in living areas has also increased in the last twenty years or so, and liberal Democrats are becoming more likely to live near other liberal Democrats, etc . This trend might be surprising to some, as Democrats and Republicans are traditionally portrayed as diametrically-opposed forces. But if polarization is only defined as the difference between group ideological or issue positions, it doesn’t appear to have been occurring in the past several decades in America. Polarization may instead simply be a misnomer for “political sorting.”
However, many people would instinctively disagree with this conclusion. They feel rising tension in our modern political environment and likely attribute it to differences (read: disagreements) between Democrats and Republicans, liberals and conservatives. Since differences in issue positions can’t explain this tension, some political scientists focus not on issue consistency or other types of sorting to describe polarization but rather on the behavioral effects of that sorting. Sorting of politically associated identities — party, ideology, issue positions, living area, demographics — in individuals has been known to increase their affective polarization, or their active dislike for opposing political groups (and reciprocal loyalty to their own group) . In fact, even the perception of demographic sorting in political parties may increase affective polarization in those who hold that perception .
These results hint at how sorting is related to the more tangible aspects of polarization, namely anger, distrust, and stubbornness. As more Democrats become liberal (this does not mean the same thing as “Democrats become more liberal”), more Republicans become conservative. Similarly, if more liberal Democrats move to one place while conservative Republicans move to another, or more people of different races or religions join the same party as other people of their race or religion, people begin to get more angry at the political group that is not their own, and they become more willing to fight for their own group. This does not mean that they hold very different beliefs about the world than members of the other group; it just means that they hold different, heavily sorted group identities. Given these differences in sorted group identities, we shouldn’t be surprised that tension fills our political arena