tactical voting
noun [ U ] uk/ˌtæk.tɪ.kəl ˈvəʊ.tɪŋ/ us/ˌtæk.tɪ.kəl ˈvoʊ.t̬ɪŋ/
策略性投票（为防止另一政党赢得选举而把票投给自己并不支持的一个政党）
the act of voting for a political party or person that you would not usually support in order to prevent another party or person from winning