反はん対たいに回まわる

expression, godan verb (-ru)

go into opposition; turn against; side with the opposition

Used when someone switches sides or takes a stance against a person, group, or plan they previously supported or were neutral toward.

• 彼かれは突とつ然ぜん反はん対たいに回まわって、私わたしたちの計けい画かくを批ひ判はんし始はじめた。

  He suddenly turned against us and started criticizing our plan.

• その議ぎ員いんは与よ党とうから野や党とうへ反はん対たいに回まわった。

  The lawmaker went over to the opposition from the ruling party.