Under what conditions does the European Union (EU) promote good governance? Focusing on the EU members in Central and Eastern Europe (CEE), I present the first systematic analysis in the literature based on longitudinal data suggesting state performance varies across two indicators of governance: While there has been a general trend of backsliding in corruption control since EU accession, various time series analyses reveal no such tendency regarding ethnic minority rights. I argue that the EU has the ability to offer electoral incentives/opportunities to opposition parties in national legislatures to adopt pro-EU policy preferences, which pressures government parties to implement reforms demanded by the EU. Several statistical models suggest that such political leverage the EU has over national governments is a stronger explanation for the cross-issue variation than any other alternative in the literature including the popular ‘membership conditionality’ argument. More specifically, prior to membership, the EU offers electoral incentives to opposition parties in CEE and mobilizes them to pressure governments to fight corruption. Yet, following accession, parties move away from EU-induced policies. Regarding minority protection, pro-minority opposition parties empowered by the EU during candidacy continue to favor pro-minority policies after accession and push governments accordingly.