Doug McAdam and Karina Kloos are the authors of Deeply Divided: Racial Politics and Social Movements in Postwar America (Oxford University Press, 2014). McAdam is The Ray Lyman Wilbur Professor of Sociology at Stanford University and the former Director of the Center for Advanced Study in the Behavioral Sciences. Kloos is a scholar of political sociology and social movements at Stanford University, where she is a PhD candidate.

What has gotten us to this point of high political polarization and high income inequality? McAdam and Kloos offer a novel answer to what divides us as a country that focuses on the role social movements have in pulling parties to the extremes or pushing parties to the middle. They argue that the post-World War II period was unusual for its low levels of social movement activities and the resulting political centrism of the 1950s. The Civil Rights movement that followed – and the related backlash politics of the Southern Democrats – pushed the parties away from the center and toward regional realignment. Along the way, activists re-wrote party voting procedures that reinforced the power of vocal minorities within each party, thereby entrenching political polarization for the decades to come.