Sunday's victory by an anti-nuclear activist in the Niigata gubernatorial election is a setback for Prime Minister Shinzo Abe's energy policy.

Ryuichi Yoneyama, 49, defeated the candidate endorsed by Abe's Liberal Democratic Party. Former construction ministry bureaucrat Tamio Mori, 67, was expected until the last moment to cruise to victory.

Yoneyama, a doctor and lawyer, has never held office.