SEOUL, South Korea — An appeals court in South Korea sentenced a former presidential hopeful to three and a half years in prison for sexual assault on Friday, overturning a lower court’s acquittal in a case closely watched by supporters of the #MeToo movement.

The politician, Ahn Hee-jung, is the best known among a number of public figures who have been accused of sexual misconduct since the #MeToo movement gained force in South Korea early last year. A lower court in Seoul acquitted Mr. Ahn last August, saying there was not enough evidence to support the charges against him.

But the Seoul High Court threw out that ruling on Friday, convicting Mr. Ahn of raping his secretary, Kim Ji-eun, at least nine times between July 2017 and last February, while he was governor of South Chungcheong Province.

Mr. Ahn, 53, was arrested and taken to prison. He has a week to file an appeal to the Supreme Court.