Coalition theories provide a basis for making predictions about several aspects of coalition formation, including the composition of the government and the distributional payoffs between coalition partners. Empirical research on the distributional side of coalition bargaining has focused mainly on the allocation of ministerial portfolios, and to a lesser extent on the negotiated policy package contained in the coalition agreement. Assuming that parties care about policy, the most direct measure of distributional payoffs is the actual success of coalition parties in implementing their policies, rather than in their ability to secure ministerial posts or to shape the coalition agreement. To date, this question has been neglected in the literature. Using comparative data on election pledge fulfilment, this paper examines the success of parties in coalition governments in implementing their policy programmes. The goal is to test competing hypotheses regarding the factors that shape the relative bargaining strength of coalition partners.
