AI 中文总结
本文研究政党最大化立法权力的选举竞争模型，刻画了两党、三党、四党制下的对称纯策略均衡，发现更严格的联盟通信会产生向心力量，极限下中位数选民定理仍成立。
AI 中文摘要
本文研究了一种选举竞争模型，其中政党最大化的是立法权力而非选票份额。选民均匀分布在单位区间上，会投票给提出最接近政策纲领的政党。选举后，政党通过由意识形态接近性产生的通信网络组建联盟：若两个政党的政策距离至多为$d$，则它们直接相连。政党的目标是其在由此产生的图受限投票博弈中的迈尔森值。本文刻画了两党制、三党制和四党制下的对称纯策略均衡。两党制会产生向中位数收敛的结果；三党制存在连续统的对称均衡，其中两个极端政党直接相连；四党制的唯一对称均衡是两个政党位于$(1-d)/2$，另外两个位于$(1+d)/2$。在三党制和四党制中，由更小的$d$代表的更严格的联盟通信会产生向心力量，尽管是多党环境，在极限情况下中位数选民定理仍然成立。
英文摘要
This paper studies an electoral competition model in which parties maximize legislative power rather than vote shares. Voters are uniformly distributed on the unit interval and vote for the party proposing the closest policy platform. After the election, parties form coalitions through a communication network arising from ideological proximity: two parties are directly linked if their policy distance is at most $d$. A party's objective is its Myerson value in the resulting graph-restricted voting game. I characterize symmetric pure-strategy equilibria in two-, three-, and four-party systems. The two-party case yields convergence to the median. The three-party case admits a continuum of symmetric equilibria in which the two extreme parties are directly linked. In the four-party case, the unique symmetric equilibrium places two parties at $(1-d)/2$ and two parties at $(1+d)/2$. In both three- and four-party systems, more restrictive coalition communication, represented by a smaller $d$, generates a centripetal force, and the median voter theorem holds in the limit despite the multiparty setting.
