This article explores the potential role of political parties in international politics. It argues that political parties can fulfil crucial legitimating functions for international political arrangements that are not easily substituted for. In particular, I submit that parties are essential in: structuring and articulating political ideas; mobilizing citizens and support; and selecting political leaders. Without political parties, these functions remain underdeveloped in international organisation and fail to be connected to the peoples whose interests they are ultimately supposed to serve. Notably, however, thus far parties hardly figure in theories of democratic international governance. These theories rather feature states (intergovernmentalism), procedural checks and balances (liberal institutionalism), international law (cosmopolitanism) and social movements (deliberative approaches) as the key international institutions. In contrast, as this article underlines that political parties perform a unique role in linking particular interests to the common good, it calls for a further theorizing of the potential of political parties in the overlapping and interacting political institutions that constitute the emerging global polity.
