swing voter
noun🔊/ˌswɪŋ ˈvəʊtə(r)/
🔊/ˌswɪŋ ˈvəʊtər/
(North American English) (British English floating voter)
a person who does not always vote for the same political party or who has not decided which party to vote for in an election 摇摆选民（不确定投哪一政党的票）