Saturday's chaotic U-turn, after a failed attempt to replace Kim with former Prime Minister Han Duck-soo, underscored the People Power Party's leadership crisis following the ouster of former president Yoon Suk-yeol over his martial law imposition in December, which possibly doomed the conservatives' chances of winning another term in government.
Kim, a staunch conservative and former labour minister under Yoon, was named the PPP's presidential candidate on May 3 after winning 56.3 per cent of the primary vote, defeating a reformist rival who had criticised Yoon's martial law.
But the PPP's leadership, dominated by Yoon loyalists, has spent the past week desperately pressuring Kim to step aside and back Han, whom they believe stands a stronger chance against progressive Democratic Party frontrunner Lee Jae-myung.
After talks between Han and Kim failed to unify their candidacies, the PPP's emergency committee took the unprecedented step early on Saturday of nullifying its primary, cancelling Kim's nomination and registering Han as both a party member and its new presidential candidate.
However, the replacement required approval through an all-party vote conducted through an automated phone survey, which ultimately rejected the switch on Saturday night.
"While we cannot disclose the figures, the vote on switching the candidate was rejected by a narrow margin," party spokesman and lawmaker Shin Dong-wook said.
Kim, who had denounced the party's attempt to replace him as an "overnight political coup," was immediately reinstated as the candidate and plans to officially register with election authorities on Sunday.
"Now everything will return to its rightful place," Kim said in a statement.
Kim, 73, was a prominent labour activist in the 1970s and 80s but joined a conservative party in the 1990s, saying he gave up his dream of becoming "a revolutionist" after witnessing the collapse of communist states.
Since then, he has served eight years as governor of South Korea's Gyeonggi province and completed three terms in the National Assembly.
Han served as acting president after Yoon was impeached by the legislature in December and officially removed by the Constitutional Court in April.
He resigned from office May 2 to pursue a presidential bid, arguing his long public service career qualifies him to lead the country amid growing geopolitical uncertainty and trade challenges intensified by the policies of US President Donald Trump.
Han, who had called for unity after being promoted as the candidate, said in a statement that he "humbly accepts" the voice of party members.
Han and Kim have lagged well behind Lee in recent opinion polls.
Lee, who spearheaded the Democrats' efforts to oust Yoon, ridiculed the PPP efforts to switch candidacies, telling reporters on Thursday, "I have heard of forced marriages but never heard of forced unity".
