Grand coalitions under power sharing unicameralism: From a case of Schleswig-Holstein via combinatorial analysis in German federal states

Grand coalitions should not be expected in a parliamentary system. It is suggested by not only a classical office seeking theory, but also a normative perspective which focuses on accountability and responsibility of individual political parties. Empirically, this thesis is supported from unicameral two-party systems. Grand coalitions may be formed under bicameral multi-party systems, but the institutional- and structural condition based causal path(s) is still theoretically or normatively possible to explain otherwise. However grand coalitions are not unusual in Germany and Austria whose party systems are basically constructed by two blocks since 1950s. And a feature of ‘the grand coalition state (Schmidt 2009)’ is mirrored in the autonomous subnational level, i.e. in the unicameral two-party systems. To explain why political parties in the federal states seek to form them, following three conditions can be understood as an analytical start point: (1) a convergence of party strategies in multi-level settings, (2) proportional systems in Austrian federal states, (3) and a communist heritage of East Germany. In case of a German federal state, Schleswig-Holstein 2005, however a grand coalition was realised without the above structural-, institutional- and contextual conditions. From the unexplainable case, a special form of unicameralism will be identified, namely power sharing unicameralism between parliament majority and minority. Based on the case study, this paper finally attempts to formulate a conjunctural hypothesis via a combinatorial analysis in 16 German federal states; grand coalitions can be expected, if the institutional condition i.e. power sharing unicameralism is combined with polarisation and bargaining power fragmentation.