本研究從民眾認知外在威脅的觀點，分析其在2020年的總統選舉中，如何影響其投票行為。在2019年的年初，中國國家主席習近平提出「一國兩制，台灣方案」之後，蔡英文總統給予強力的回應，伴隨同年六月間香港升高的「反送中運動」，讓中華民國會不會因為中國大陸的威脅而消失的「亡國感」發酵，成為影響2020年選舉的重要關鍵。本研究運用在2020年的選舉前後執行的定群追蹤調查，分析民眾是否具有「亡國感」的感受。我們發現，擔心因為被中國大陸統一而讓中華民國消失的民眾比較較高，超過五成一。我們進一步檢視，擔心中華民國被中國大陸統一而消失者，以年輕民眾、教育程度較高者以及傾向獨立者的比例較多。民眾具有「亡國感」者，更傾向在2020選舉中支持蔡英文總統。因此，民眾感受到的外在威脅，極有可能在選舉中發酵，進一步影響民眾的投票抉擇。我們認為：透過對民眾對外在威脅的感受之分析，讓我們更能理解選民的投票決定。

From the perspective of possible external threat, this study analyzes how voters' perceptions of external threat might affect their vote choice in the 2020 Presidential election in Taiwan. After Chinese President Xi Jinping proposed the "'one country, two systems' Taiwan formula" in January of 2019, President Tsai Ing-wen gave a strong response. Along with the "Anti-Extradition Movement" in Hong Kong in June of the same year, the "sense of national subjugation (wangguo gan)" fermented by the possible threat from the mainland China has become an important factor to influence the 2020 election. This study uses a panel study conducted before and after the 2020 election to analyze whether people have a "sense of national subjugation." We found that the proportion of people worried about the disappearance of the Republic of China due to the unification of mainland China is relatively high, exceeding 51%. We further examine, those who worried about the disappearance of the Republic of China by the reunification of mainland China are young people, those who with higher education levels and preferring to support Taiwan independent. People with wangguo gan are more inclined to support President Tsai Ing-wen in the 2020 election. We believe that through the analysis of people's perception of external threat, we will have better understanding of how voters make up their vote choices.