ABSTRACT
This chapter investigates the three social effects of polarization on congressional behavior and the responses by three presidencies (Bush, Obama, Trump) to accommodate domestic and international expectations of U.S. leadership at critical junctures during the Iran nuclear crisis. Tracing the process of U.S. leadership role-taking in the Iran case exposes a dramatic divergence between both parties about how security goods should be achieved and distributed internationally. The chapter describes four phases in which polarization severely intensified the degree of diagonal contestation between Congress and the executive branch, from role dissonance and intra-role conflict up to congressional consideration of the Iran Nuclear Agreement Review Act, to an outright inter-role conflict and crisis after the Iran nuclear accord was negotiated. The Iran nuclear crisis proves to be constitutive to a changing U.S. leadership role towards allies and partners, as well as the changing relationship between both branches of power in the field of nuclear nonproliferation. Inter-role conflict has been coped with by the Trump administration by further polarizing the domestic environment and making U.S. leadership more ego-centered. An original data set was developed for the analysis, consisting of congressional debates, co-sponsorship alliances, as well as ideological scores.
