The 2016 presidential election brought to light the increasingly polarized nature of American politics. What brought about this political extremism, and can anything be done to curb it? This volume helps to define political extremism, explores the ways in which extremism manifests itself, including hate speech and domestic terrorism, and explains theories about how it can be counteracted. With partisanship in the United States showing no sign of decline without significant intervention, it is more essential than ever to try to understand what brought about this political division.