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）