Scholars have paid increasing attention to democratic backsliding, yet efforts to explain this phenomenon remain inchoate. This article seeks to place the study of democratic backsliding on sturdier conceptual, operational, and theoretical foundations. Conceptually, the challenge of backsliding is to define changes that take place within a political regime. Methodologically, the challenge involves measurement of intraregime changes, as alternative coding schemes change the population of units that have experienced democratic backsliding. Theoretical challenges are dual: First, despite a rich and diverse literature, we lack readily available theories to explain backsliding, and second, the theoretical debates that do exist—centered on the causes of democratic transitions, democratic breakdowns, authoritarian resilience, and democratic consolidation—remain unresolved. We consider how these theories might be called into service to explain backsliding. By doing so, the article aims to set the terms of the debate to create a common focal point around which research can coalesce.