Like never before, the conflict over the restructuring of the German welfare state has shaken the relationship between social democracy and trade unions. Is the Agenda 2010 the cause of a rift in the traditional alliance of the labor movement? And to what extent has the network of relationships between the parties and trade unions been realigned as a result? With Christian Neusser's analysis of party-union relations, there is now a study that examines the relationship with trade unions for all four welfare state parties - SPD, CDU, Bündnis 90/Die Grünen, and Die Linke. The author outlines historical development lines, analyzes commonalities and differences in the interests of the actors, as well as their mutual organizational entanglements, and investigates political interest representation at the parliamentary-institutional level.