South Korea's conservatives made another about-face on Saturday and reinstated their nominee, just hours after dropping him and reopening the nomination process as the divided party struggled for unity to challenge the liberal frontrunner in a presidential election four weeks away.

Lee Jae-myung has been the front-runner in South Korea's presidential election, but his candidacy has been complicated by criminal trials he has decried as politically motivated.

Former Prime Minister Han Duck-soo said Wednesday he would make reforming South Korea's constitution his top priority if he is able to secure the candidacy of the conservative People Power Party and win the presidency.