The paper analyses the role played by the European political families in the 2007 enlargement with Bulgaria and Romania. As this last enlargement round was also the most difficult for the EU to date, and the European Parliament played an increasing role in the process, the importance of party political affiliation became paramount for the success of the accession negotiations. The paper argues that engagement with the EU political families became part of the “tracks-based” negotiation model followed by the candidate states. This particular type of political engagement is contrasted with other negotiation strategies followed by previous candidate states.