Downsian Competition for the Myerson Value∗
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摘要
This paper studies an electoral competition model where parties maximize legislative power via the Myerson value rather than vote shares. Voters are uniformly distributed on [0,1], and each voter supports the closest policy. A coalition-communication graph emerges: two parties link if their policy distance is at most d, and a party’s payoff equals its Myerson value in the graph-restricted voting game. The analysis derives symmetric pure-strategy equilibria for n = 2, 3, 4. In the two-party case, the unique equilibrium converges to the median (unaffected by d). In the three-party case, a continuum of equilibria exists as long as the two extremes communicate; as d → 0, the median voter theorem holds. In the four-party case, the unique symmetric equilibrium places two parties at (1−d)/2 and two at (1+d)/2; as d → 0, convergence to the median occurs. Across 3- and 4-party setups, tighter coalition communication (smaller d) exerts a centripetal force toward the center. An application with two extreme parties shows endogenous cordon sanitaire behavior and again median convergence as d → 0. These results highlight the role of coalition-power incentives in multiparty policy competition and the tractability of the Myerson value as a bargaining power measure [page::0][page::8][page::9][page::10]
