The author deals with the course and results of conflicts between the political partners PDS and SPD in three German federal states during the period 1998 to 2004. On a broad source base, he examines seven policy-related and three person-related conflicts between socialist PDS and social democratic SPD in Saxony-Anhalt, Mecklenburg-Western Pomerania and Berlin. The central question is which factors were decisive for the assertiveness of the smaller partner, the "Party of Democratic Socialism," during conflicts within so-called "red-red" alliances. The second question is whether and how the decision makers of cooperating political parties can prevent the occurrence of confidence crises between their central alliance players. In Addition, the study takes a look at important periods of state politics in two East German Regions and in the city of Berlin 10 years after the fall of the Berlin Wall. As part of the research, 25 key players of regional politics were interviewed.