Brakeman or booster? Presidents, ideological polarization, reciprocity, and the politics of US arms control

US arms control policies have shifted frequently in the last 60 years, ranging from the role of a 'brakeman' regarding international arms control, to the role of a 'booster,' initiating new agreements. My article analyzes the conditions that contribute to this mixed pattern. A crisp-set Qualitative Comparative Analysis (QCA) evaluates 24 cases of US decisions on international arms control treaties (1963-2021). The analysis reveals that the strength of conservative treaty skeptics in the Senate, in conjunction with other factors, has contributed to the demise of arms control policies since the end of the Cold War. A brief study of the Trump administration's arms control policies provides case-sensitive insights to corroborate the conditions identified by the QCA. The findings suggest that conservative treaty skeptics contested the bipartisan consensus and thus impaired the ability of the USA to perform its leadership role within the international arms control regime.