選區規模對政黨競爭的影響

Abstract

杜瓦傑法則(Duverger’s Law)自1950年代以來，歷經半世紀以上的辯證，仍舊是探索選制政治影響的重要依據。細究杜瓦傑法則適用情形的討論與修正大多強調選區個案的特殊性，其中包含選區規模(district magnitude)與地方傳統勢力與政黨組織能力等。在複數選區單記不可讓渡投票制(SNTV)下，選區規模愈大時，小黨固然比較有機會取得席次，但這也不一定代表大黨會因此失去選舉優勢，畢竟小黨大多僅在特定選區有獲取席次的實力，但如果以全國層次來觀察時，小黨在更多選區的實力顯得不足，此種實力分布上的差異也使其在最後議會的席次與大黨產生更大差距。同樣的，有利席次最大化的競選策略需要長期經驗的累積，尤其是如何因應提名與配票的挑戰，大黨往往比小黨有更多的資源可以因應，也讓大黨比小黨擁有比較大的優勢。本文將以2014年直轄市／縣市議員選舉作為背景資料，除了探討2018年的地方議員選區規模與政黨命運之間的關係，為地方選舉候選人提供若干啟示之外，亦關切台灣特有的地方政治生態對類似「選區規模越大對小黨越有利」傳統論點的挑戰。本文雖透過卡方檢定與多元迴歸模型的統計分析，驗證了選規模的影響力，但亦證實了選區規模對政黨選舉表現的影響力會因地方傳統政治的不同而有所差異，其中以國民黨最為明顯。綜合分析結果，本文遂提出「規模越大對小黨越有利」應修正為「規模越大對選區內選舉情勢相對弱勢者越有利，但選區內最大黨仍舊保有優勢」的論點。

To date, Duverger`s Law is still a crucial foundation to explore political influence of the election system after more than half a century of dialectic verification since the 1950s. Most of the discussions and amendments on the application of Duverger’s law emphasize the discrepancies between different districts, including district magnitude, local traditional forces and party organizational capability. Under the Single Non-Transferable Vote (SNTV) electoral system employed by the multi-member constituency elections, the minor parties are more likely to win more seats in greater district magnitude. However, it does not necessarily imply that the big parties will lose their electoral advantage. Although minor parties are able to win seats in particular districts, they still appear to be comparably weaker in more districts in the national level, which then put them further behind the big parties in parliament. Similarly, the electoral strategy of maximizing the number of advantageous seats requires the accumulation of long-term experience, especially in dealing with the challenges of nomination and vote equalization. Accordingly, big parties have more preponderance than minor parties in terms of resources, giving them a bigger advantage over the minor parties. Based on the municipal and city/county councilor elections in 2014, the current paper discusses the size of district magnitude and the fate of political parties to shed some light for local election candidates in the 2018 elections. The challenges of traditional theory such that “greater district magnitude favors minor parties” will be re-investigated in accordance with Taiwan’s unique political ecology. Results of Pearson’s chi-squared test and multiple regression analysis have shown the significant effect of district magnitude. It has also revealed that the influence of district magnitude on party election performance varies with the difference of traditional local politics, in which the Kuomintang experienced the most significant impact. The main finding of this paper paper indicates that the theory “greater district magnitude favors minor parties” should be amended into “greater district magnitude favors relatively disadvantaged miorn parties at the district level, but the biggest party continues to prevail.”