When we first began collaborating on a strategic spatial model of parliamentary government in 1988, we were struck by two patterns in the professional literature. In the United States, theories of political coalitions, close to the mainstream in the 1960s largely due to the impact of Riker's important book (Riker, 1962), had been relegated to a quiet tributary by the mid-1970s. The American modeling community had turned its attention to institutionally enriched models, with special emphasis given to the institutions of the U.S. legislature and executive. On the other side of the Atlantic, coalition theory was alive and well, principally as an empirical enterprise applied to European parliamentary democracies. This apparent divergence in interest and emphasis stimulated us to think about how to apply institutional models of politics to the making and breaking of European coalition governments. It was our strong belief that there was nothing in principle distinctively “American” about such institutional models, despite the fact that in practice such models had been applied primarily to American institutions. The result is the present volume, an exercise in intellectual and geographical arbitrage.

Part I of this book lays out the institutional context of government formation in parliamentary democracies. In any parliamentary democracy, there is always an incumbent government – by which we mean a cabinet seen as an allocation of ministerial portfolios. The incumbent government remains in place until supplanted by some alternative. Parliamentary parties with policy preferences, bargaining reputations, a stable of senior politicians and a strategic weight determined by their proportion of legislative seats, continually assess and reassess the sitting cabinet.