Explaining the 2005 Coalition Formation Process in Germany: A Comparison of Power Index and Median Legislator Approaches

Abstract

The article uses data from the 2005 German Bundestag elections to test the power index (PI) and median legislator (ML) models of coalition formation. The article finds that, while the PI approach is successful in predicting the real‐world formation of a Grand Coalition after the election, neither model is sufficient to explain the outcome of the coalition formation process. Nevertheless, the article argues that such formal models are useful in identifying ‘crucial cases’ and in eliminating irrelevant data from explanations. The article concludes by suggesting some methodological routes through which formal models can be harnessed to culturally sensitive, inductive research.

The Grand Coalition and the Party System

“…Thus, within the real-world constraints of German politics and in the absence of individual defections from one party to another, minimal winning coalitions are subject to 'swing' 51 when both parties in a two-party coalition or at least one party in a multi-party coalition are able to transform a winning coalition into a losing coalition by its defection from a coalition (or vice-versa) 52 . At the same time, however, not all feasible coalitions are minimal winners and it is often the case that that these are subject to swing as well.…”