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.

South Korea's Supreme Court said it will rule on Thursday in a criminal case that could determine whether the frontrunner for the June 3 snap election, former opposition party leader Lee Jae-myung, can run for president.