crossover vote

(US, politics) The casting of a crossover vote.

A US political term for the practice of a registered voter participating in the primary election of a different party than the one they belong to — or, in open primary states, strategically voting for a weaker opponent to influence the other party's nominee. Crossover voting is legal in most US states with open or semi-open primaries and is a recurring subject of strategic debate during election cycles. Critics argue it distorts primary results; defenders see it as a legitimate form of civic participation.

(chiefly, US, idiomatic, politics) To vote, unite, or otherwise co-operate with members of another political party in order to achieve governmental or political action.

(chiefly, British, and, Canada, idiomatic, politics) Of a member of a parliament, to resign from one's political party and join another party, resulting in moving from one's currently assigned desk or seat in the legislative chamber to a new desk or seat physically located with the other members of one's new party.

(North America, informal) To double-cross or betray (someone).