floating voter
noun🔊/ˌfləʊtɪŋ ˈvəʊtə(r)/
🔊/ˌfləʊtɪŋ ˈvəʊtər/
(British English) (North American English swing 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 游离选民（不确定投哪个政党的票）