摘要 : This article proposes a game-theoretic setting to explain the fragmentation of majority and opposition coalitions in governments. The model is two-stage: (1) the leaders of each coalition control the size of the parties in their g... 展开 This article proposes a game-theoretic setting to explain the fragmentation of majority and opposition coalitions in governments. The model is two-stage: (1) the leaders of each coalition control the size of the parties in their group so as to maximize the political power of their coalition, and (2) the political party leaders in each coalition decide their degree of participation in their coalition's collective action. The main conclusion is that the concentration in the two opposing coalitions will be related when the competition between them is fierce. This is shown to hold for the Left-wing and Right-wing coalitions in French local governments, revealing competition in fragmentation in these coalitions. 收起