For more than two decades political scientists have discussed rising elite polarization in the
United States, but the study of mass polarization did not receive comparable attention until
fairly recently. This article surveys the literature on mass polarization. It begins with a
discussion of the concept of polarization, then moves to a critical consideration of different
kinds of evidence that have been used to study polarization, concluding that much of the
evidence presents problems of inference that render conclusions problematic. The most …