Why are some new political parties successful at creating mass partisanship and engendering stable electoral support, while most fail to take root in society and disappear quickly? Creating Partisans unveils the secrets behind successful political parties, taking a deep dive into the formation and success of new political parties in Latin America. Based on extensive fieldwork and using a multi-method approach, the book explores how different mobilization strategies sway voters to support new parties. While prior studies have focused on the various types of direct appeals parties make to voters, Creating Partisans reveals that it is organizationally mediated appeals - those that engage voters through locally-based civil society organizations - that can secure electoral support more effectively and can create lasting partisan attachments. From indigenous organizations to informal sector unions, new types of societal organizations play a critical mediating role in shaping electoral outcomes and fostering long-term partisan loyalties in young democracies.