Abstract: The European Union’s quest for democratic and legitimate governance, together with an appropriately defined collective identity and boundaries did not start with the current enlargement process. The Union’s search for its finalité politique and collective identity, however, will be the determinant factor regarding its final decision on Turkey’s membership. This study argues that rather than the size and economic, political and social problems of the country, its factual or perceived divergent identity will influence the course of Turkey-EU relations. The impact of enlargement on European democratic governance and collective identity is analyzed, in this regard, with a view to highlight Turkey’s special case status and an analysis of Turkey’s impact on European governance from a democracy/legitimacy vs. efficiency perspective is undertaken. In that context, various approaches to the conceptions of collective political identity and constitutionalisation in the EU are examined with a special emphasis on constitutional patriotism, constitutional tolerance, and pluralism/particularism in order to determine the consequences of each option for a viable integration between Turkey and Europe.