EU enlargement policy has long been hailed as the most effective form of external democracy promotion. Yet in recent years, democratic backsliding has emerged both among new member states and in current candidate countries. Why do we see such trends? I argue that unintended side effects of EU policies, but also shifts in the broader international context can account for the reduced effectiveness of EU democracy promotion. Focusing on the interaction between conditionality, domestic preferences, and the rise of authoritarian alternatives helps explain the puzzling lack of deep democratisation in the Western Balkans region. In short, credibility is key both for preventing democratic backsliding and for countering it once it has emerged.