Challenging and transforming political institutions has long been recognized as central to feminist projects of change. Existing institutions can be reformed and/or new institutions created. Over several decades, feminist political scientists, activists, and equality-seeking states have addressed questions of how the existing institutions of governance—global, regional, and local—work in gendered ways and how they can be reformed or redesigned to incorporate gender justice and promote gender equality and women's human rights. We now have a wealth of case studies about efforts to insert new actors, new rules, and new ideas into old institutions. Work has focused on three trends in institutional reform: the adoption of gender quotas, which aim to transform the institutions of political recruitment (see, for example, Franceschet, Krook, and Piscopo 2012; Krook 2009); the creation of women's policy machinery; and the introduction of gender mainstreaming, the last two of which aim to counteract the traditional mobilization of masculinist bias in the institutions of legislation and policy making (see, for example, McBride and Mazur 2010, Squires 2007, True 2003). However, this rich field of research presents us with a puzzle: On the one hand, there's been a rapid proliferation and remarkable diffusion over the past 30 years—for example, quotas (of one form or another) have been adopted in more than 100 countries. On the other hand, however, there have been variable and sometimes unpredictable outcomes in practice, highlighting the difficulty of inserting new claims into old institutions.