Leader ideology and state commitment to multilateral treaties

The existing literature argues that the left is generally more supportive of multilateralism in foreign policy than the right. However, the impact of ideology on state commitment to multilateral cooperation have not yet been empirically tested adequately. We assess the presence of such a left-right divide on state commitment to multilateral treaties employing an original dataset, containing all the available information about the ratification of the multilateral treaties deposited with the UN Secretary General since 1945. Our results indicate that indeed countries led by left-wing leaders are generally faster at ratifying treaties than those led by right-wing leaders. However, the association between leader ideology and commitment to multilateral treaties is substantially conditioned by regime type and the international context. In fact, we find robust evidence of a significant gap in ratification duration between states led by left-wing and right-wing leaders in democracies but not in other regime types, and during the Cold War but not after. Through such findings, this article provides a contribution to the debate on the impact of ideology on international relations and the drivers of global support for multilateralism.