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.

SEOUL (Reuters) - South Korea's conservatives dropped their presidential candidate on Saturday and reopened a process to pick a new nominee as the country's former prime minister joined the party to challenge a liberal frontrunner less than four weeks before the election.

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.