选举竞争下政党分化的动态模型

中文摘要 AI 辅助

为什么当大多数选民仍处于中间立场时，政党却会出现极化？超越传统的基于点状的模型，我们通过开发一个空间投票框架来解决这一经典难题，该框架将政党概念化为连续的意识形态分布。在内生投票参与下，这些政党调整其定位，以最大化总票数和议会代表权的组合。我们证明，这一理论表述揭示了多党竞争中的一个显著相变，从向心收敛转向离心分离。这两个目标并不必然奖励相同的政党移动方向，因为选民只为意识形态上可接受的政党投票。数值结果描绘了这一转变的精确边界：更高的政党数量会破坏中间派均衡并扩大分化区域，而显著的党内分散和对代表权的更强重视则会收缩该区域。此外，选举制度关键性地控制着这种分化：当选民偏好因地理选区而异时，相同的全国选民群体可以根据选票如何转化为席位而触发完全不同的相变。总之，我们的结果表明，政党分化是从选举竞争本身的动态中内生地涌现的。小的初始差异是增长还是衰减，不仅仅是选民偏好的反映，而是由政党目标、竞争者数量、党内宽度和选票到席位的转换规则所决定的结果。

英文摘要

Why do political parties polarise when most voters remain in the centre? Moving beyond conventional point-based models, we address this classic puzzle by developing a spatial voting framework that conceptualises political parties as continuous ideological distributions. Operating under endogenous turnout, these parties adapt their positioning to maximise a combination of total votes and parliamentary representation. We demonstrate that this theoretical formulation reveals a distinct phase transition in multiparty competition, moving from centripetal convergence to centrifugal separation. These dual objectives do not necessarily reward the same directional party movement as voters only cast ballots for ideologically acceptable parties. The numerical results map the precise boundaries of this transition: a higher party count destabilises the centrist equilibrium and expands the zone of divergence, whereas pronounced internal party dispersion and a stronger emphasis on representation contract it. Furthermore, electoral institutions critically govern this divergence: when voter preferences vary across geographic districts, the same national electorate can trigger entirely different phase transitions depending on how votes are converted into seats. Together, our results show how party differentiation emerges endogenously from the dynamics of electoral competition itself. Whether small initial differences grow or decay is not merely a reflection of voter preferences, but an outcome dictated by party goals, competitor count, internal party breadth, and vote-to-seat conversion rules.

发表机构

• Trinity College Dublin（都柏林三一学院）
• Beijing Normal–Hong Kong Baptist University, Zhuhai（北京师范大学-香港浸会大学联合国际学院）

机构由 AI 辅助整理，请以论文原文为准。