Chapter 2 lays out the theory of the book, providing a broad overview of political science’s extant understanding of partisanship across diverse fields of study. It lays out the theory in three parts. First, it creates a framework for understanding how opposition partisanship and ruling party partisanship are unique social identities in electoral autocracies. Citizens who identify as partisans hold specific political beliefs that are common across all electoral autocracies (but not democracies). Second, it argues that these identities are produced at a grassroots level through a process of political socialization that occurs between friends and within families. Finally, the third part of theory argues that partisan social networks are fundamentally rooted within the unique political geography of electoral autocracies and elucidates a framework for understanding this geography, as well as its broader effects on beliefs about democracy and political legitimacy in such regimes.