How and under which conditions have European regional organizations been effective promoters of democratic change in Central and Eastern Europe? In this article, the author argues that only the credible conditional promise of membership in the European Union and NATO has had the potential to produce compliance with liberal-democratic norms in norm-violating transformation countries. These incentives, however, were not sufficient when the power costs of compliance were high for the target governments. They did little to alter the policies of authoritarian governments, which forewent the benefits of accession rather than risk losing power as a result of democratic reforms. Thus, whereas political conditionality was largely redundant in the forerunner countries of democratization in Central and Eastern Europe (except for some specific reform issues) and generally ineffective with entrenched authoritarian regimes, it proved highly effective in supporting democratic forces and locking in democratic reforms in the unstable democratic countries of the region.