ABSTRACT
This chapter develops the theoretical and methodological basis to investigate polarization’s effects empirically. The chapter first theorizes domestic contestation and international role-taking as a “two-level role game.” Diagonal contestation is a crucial component in the two-level role game as it describes instances in which equal but separate branches of power enact roles vis-à-vis each other but also towards international others. International leadership roles comprise three auxiliary roles reflecting leadership’s relationality (representative role), functionality (agenda setter role), and temporality (mediator role). On the domestic level, four distinct roles are distinguished that Congress enacts vis-à-vis the executive branch. The chapter describes four consequences diagonal contestation can produce that shape the degree to which the executive branch is capable of taking the role of the state and enacting an international leadership role. The chapter proceeds by showing that political ideologies are the central origin of role conceptions and domestic roles. Finally, the chapter lays out how, through a multi-method design, diagonal contestation and U.S. leadership role-taking are to be operationalized via an original quantitative and qualitative data set that makes polarization adaptable for foreign policy analysis and the study of international roles.
