South Korea’s acting leader, Prime Minister Han Duck-soo, says he is resigning amid reports he will run in next month’s presidential election.

South Korea’s presidential race was upended Thursday, less than five weeks until election day, when the front-runner was ordered to undergo a new trial on charges of election law violations and the nation’s acting president resigned amid speculation he will enter the field.

Prime Minister Han Duck-soo has been mulling whether to contest the election, while the main opposition candidate and front-runner suffered a setback in court.