tactical voting
英[ˈtæktɪkəl ˈvəʊtɪŋ]美[ˈtæktɪkəl ˈvotɪŋ]
In voting systems, tactical voting (or strategic voting or sophisticated voting or insincere voting) occurs, in elections with more than two candidates, when a voter supports a candidate other than his or her sincere preference in order to prevent an undesirable outcome.