noun
protest vote
A vote cast not to support a candidate but to express dissatisfaction with the options or the political situation.
今回の選挙では批判票が多く、与党は苦戦した。
In this election, there were many protest votes, and the ruling party struggled.
死票 refers to votes that do not contribute to electing a candidate (wasted votes), whereas 批判票 is a deliberate protest vote.
Compound of 批判 (criticism) and 票 (vote, ballot).