「西岸效應」與策略性投票？2018年臺北市市長選舉的空間分析

“West Coast Effect”and Strategic Voting? Spatial Analysis of the 2018 Taipei City Mayoral Election

本研究探討2018年臺北市市長選舉因為延遲投票而造成的投票轉向。在選舉過程中，現任市長柯文哲面臨來自丁守中（國民黨）與姚文智（民進黨）的嚴峻挑戰。在投票當天，當投票所於下午四點開始記票時，大多數的新聞媒體都報導了柯與丁之間的激烈競爭。最終選舉結果柯文哲以些微票數擊敗對手。對丁守中來說，這個選舉結果相當具有爭議。由於此次選舉與公民投票同時進行，導致投票時間嚴重延遲，相當一部分的選民在下午四點以後才開始投票，那時已經可以同時從新聞報導中瞭解到其他投票所的開票結果。這個開票訊息可能導致選民投票發生轉向，造成進一步的策略性棄保，影響最後的選舉結果。為檢驗丁守中的論據，本文蒐集中央選舉委員會發布的各投開票所選舉結果與完成登錄時間。透過空間迴歸（SLM和SEM）與地理加權回歸（GWR）的方法，我們發現，在村里層次，確實有些選票流動的現象，但是在整體層次，丁守中的擔憂並沒有經驗證據的支持，延遲投票對三位候選人的整體影響並不顯著。

This study explores the changes in voters' choices due to the delayed voting in the 2018 Taipei City mayoral election. During the election, the incumbent mayor, Wen-je Ko, faced strong challenges from Shou-chung Ting (Kuomintang) and Pasuya Yao (Democratic Progressive Party). When voting stations started to count votes at 4 pm, most news channels reported an extremely tight race between Ko and Ting. The final election outcome was a narrow-margined win for Ko. For Shou-chung Ting, the outcome was very controversial, as this election was held concurrently with a referendum and hence the voting time was seriously delayed. A substantial proportion of voters cast their votes after 4 pm, already aware of the results of other voting stations from news reports. This information was likely to lead to changes in voters' choices, resulting in further strategic voting and changes in the final outcome of the election. In order to examine Ting's argument, this paper collects the election results of each voting station and the registration time after the counting was completed and published by the Central Election Commission. Through spatial regressions (SLM and SEM) and geographic weighted regression (GWR), we find that at the village level, some votes indeed flowed. However, at the city level, Shou-chung Ting's concern has no empirical support. The overall impact of the delayed voting on the three candidates was insignificant.