ABSTRACT
The chapter reviews six major lessons drawn by European Union (EU) policy-makers following the 'big bang' enlargement of 2004 and 2007, which brought 12 new members into the EU. It is based on academic research about enlargement and its effects, and on the personal experience of the author, who conducted empirical research on enlargement from 1996 till 2004, was senior advisor to the Commissioner for Enlargement in the European Commission from 2004 to 2009, and, thereafter, worked on the Balkans, Turkey, and the new Member States of the EU for the Open Society Foundations in Brussels. The chapter argues that domestic politics have increasingly constrained the EU's external policies; especially by changing enlargement from an elite-led and largely consensus-based project to a much more contested one. Populist politics began to surge in both the EU and enlargement countries during the Euro and migration crises, bringing controversy to issues such as internal mobility from poorer to richer parts of the EU.
