A central tool of the European Union (EU) to promote the democratization of post-communist Europe have been the conditions it has attached to the offer of accession. Yet EU's influence varies across countries, and over time between the periods before and after accession. A key factor limiting the EU's democratizing impact are domestic costs of complying with the EU's conditionality: the more governments rely on illiberal and undemocratic means to maintain power, the less influence the EU has. Moreover, even if the domestic adjustment costs are not prohibitively high, for EU conditionality to bring about, or lock in democratic change, the positive and negative incentives relating to the benefits of EU membership have to be credible. The limited credibility of sanctions against backsliding in new members and of the reward of accession for current candidate countries in Southeastern Europe is a key explanation for the setback in the EU's democratizing role during this decade.A distinctive feature of the democratic transition in Central and Southeastern Europe after 1989 has been its close link to the process of accession to the European Union (EU). The first wave of post-communist transition studies did not focus much on this characteristic of the process of 2 democratization in East Central Europe (ECE). Instead, analyses focused predominantly on domestic factors to explain its outcome. 1 From the early 2000s, the literature has studied much more explicitly the role of international organizations, and of the EU in particular. 2 By now, the effects of the EU on democratization in post-communist Europe are certainly no longer 'a topic that remains mostly unexplored.' 3 And indeed, it is largely undisputed that the EU can potentially have a tremendous influence on post-communist transition. Here are two very different striking examples, albeit not directly with regard to democratization: the first, concerning a highly sensitive question of statehood, is the EU's ability to compel the Montenegrin leadership to set the threshold for the success of the referendum on independence at 55 percent, rather than 50 percent. Another often cited example is the June 1999 session of the Hungarian parliament that passed 152 of 180 laws without any debate since they concerned EU legislation. 4 The literature broadly agrees that the main tool through which the EU exercises this influence on domestic politics is through accession conditionality. 5 However, we have to be careful not to overstate the power of conditionality and the EU's actual impact on democratization. 6 First, while the EU's influence on post-communist democratization was arguably strongest in the period up to the enlargements of 2004 and 2007, even during this period, its causal impact varied across countries, issues and over time. The main question for this chapter is therefore: how can we explain this variation in the EU's influence on democratization? Second, and more specifically, the EU's ability to influence candidate countries may not be easily replicable among...