Political polarization is often cited as a negative, and occasionally as a competitive positive, for a democracy. Polarization in the United States has become a buzz word that occurs often in discussion about the current political climate, both online and offline. But there are also discussions about whether contemporary polarization is as polarized as people fear, and if it is, is it a cause of erosion or is it a canary in the mine shaft? Political polarization is too versatile a condition to be prescribed blame for a lack of plurality or public trust in a democracy. Putting any causal claim on polarization will be a difficult task for any researcher.
The Pew Research Center looked into polarization in American politics, and found that people who were either consistently left or right on the political spectrum pulled information from different places, rarely mixing. Interestingly enough, the left and the right do not rely on media in the same ways, for example people on the left tend to pull from several news sources while the right cite Fox News as their major news source. Despite how they ingest media, people who are consistently left or right do not have much overlap in news sources. But it is difficult to know whether this difference in information streams causes polarization, is a symptom of polarization, or perhaps connected with polarization in a larger picture of politics in the United States.
Polarization, if it is a cause, can also lead to different outcomes for a democracy, even making it more robust, in a myriad of different contexts around the world.  Polarization is not just about less centrists in a society, but a way to put a major spotlight on how democracies fair with clear ‘us vs. them’ relations among the populace. These power struggles can be present in any democracy, but democratic norms such as plurality in political representation, peaceful transitions of power and party restraint can be strained when ‘us vs. them’ mentalities are strong. But as McCoy et al find, their definition of polarization can lead to either gridlock, democratic erosion under new elites, democratic erosion with old elites or a reformed democracy. Gridlock may ring familiar for denizens of the United States, and democratic erosion under elites matches the behavior of Hugo Chavez in Venezuela, but despite the different outcomes, both cases had political leaders using polarizing language. This is either to appeal to splits already present, or create those splits in the national discourse. And democratic futures are not set, democracies can survive and even thrive after experiencing political polarization. But the factors that determine how well a country can manage polarization require future research.
In the meantime, discussions surrounding political polarization and democratic erosion, or even collapse, should exercise caution when talking about causality. Not only is the existence of a causal relationship between polarization and democratic erosion uncertain, but how polarization would affect erosion is a question that we still need to investigate.
 McCoy, Jennifer, Tahmina Rahman, and Murat Somer. 2018. “Polarization and the Global Crisis of Democracy: Common Patterns, Dynamics and Pernicious Consequences for Democratic Polities” in Special Issue on Polarization and Democracy: A Janus-faced Relationship with Pernicious Consequences. American Behavioral Scientist (62)1: pp. 16-42.
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