Mass Partisan Polarization: Measuring a Relational Concept

With recent political developments sparking sharp divisions within democracies, an understanding of the dynamics of polarization is ever more necessary. Yet we still lack the tools necessary for its comparative study at the mass level. Finding that conventional measures of polarization as ideological distance between parties or among voters do not fully capture political polarization, we develop a new index of mass partisan polarization based on support and rejection of political parties by the public. We argue that measuring polarization over political parties allows us to capture divisions over a broader range of identities or issues which parties can represent or take positions on. Using Comparative Study of Electoral Systems data, our empirical validity tests support this argument. It is our hope that this index may facilitate the further comparative study of mass political polarization on a global scale.