The shift in executive power from the European Union's member states to Brussels raises profound questions for Europe's social democratic parties as they seek to remain relevant within an integrated ""Euro-polity"". This book analyzes the response to this challenge: an entirely new organizational form of party politics emerging at the European level. The author aims to show how social democratic parties are retaining their influence on EU policymaking through a continuing process of adaptation and the evolution of an innovative party network. This network was manifested in the establishment in 1992 of the Party of European Socialists, which went on to play an important role in shaping policies at the 1996-97 IGC. He also explores what this new form of political activity means for European politics, arguing that the traditional positions of left and right may be becoming increasingly significant within the EU's evolving, transnational political culture.