Four-term lawmaker Jung Chung-rae was elected the new head of the ruling Democratic Party on Saturday.
Jung, 60, earned 61.74 percent of the votes in the national party convention held at KINTEX in Goyang, northwest of Seoul.
Jung is succeeding Lee Jae Myung as DP's leader, after Lee was elected president in June.
Rep. Park Chan-dae finished a distant second at 38.26 percent.
Votes cast by DP delegates (accounting for 15 percent) and dues-paying members (55 percent), and a public poll (30 percent) determined the new DP leader.
Jung earned 66.48 percent support from dues-paying members, 46.91 percent from delegates and 60.46 percent in the poll. In the lead-up to the convention, Jung had vowed to empower dues-paying members, a departure from an approach centered around lawmakers and delegates.
"My election is the win for DP members that yearn for the era of party member sovereignty and represents the people's wish for the success of the Lee Jae Myung government," Jung said in his victory speech. "I will serve the wishes of the people and party members, and fully dedicate myself as the DP's chairman."
Jung said he will live up to his pledge and complete reforms of the prosecution, media and judiciary before the Chuseok holiday in early October.
"As soon as the party convention ends, I will put task forces for reforms in the prosecution, media and judiciary in operation," Jung added.
The new DP leader stressed that he will stay on the same page as the president.
"The Lee administration has to succeed in order for the DP to succeed and vice versa," Jung said. "I will do everything I can as the party chairman to make sure the party, the government and the president all move as one team. I will offer my strong support for President Lee Jae Myung so that he can concentrate solely on running the nation. I will be out there doing the dirty work."
The opposition People Power Party congratulated Jung on his election and urged him to respect the PPP as a partner.
PPP spokesperson Kwak Kyu-taek described Jung as "a noted hard-liner even within the DP" and said the PPP is concerned that Jung may keep trying to rally his hawkish supporters and take a contentious stance when dealing with the opposition party.
"If the DP concentrates on devising policies to bring the people together and improve their livelihoods, rather than on waging political wars, then the PPP will offer unconditional cooperation for the people's lives and national interest," Kwak said.
Jung said he does not see the PPP on equal terms as a political party because of its ties to former President Yoon Suk Yeol, impeached and removed from office after his failed bid to impose martial law.
An outspoken critic of Yoon, Jung said the ex-president has not been sufficiently repentant for leading an insurrection, and argued that Yoon and his supporters "must be severely punished."
"The insurrection is not over yet," Jung said. "An instance such as this insurrection, brought on by Yoon Suk Yeol's martial law imposition, must never be repeated here."
Jung said the ongoing investigations by the special counsel team on Yoon's insurrection charges could expose PPP members who aided and abetted the ex-president's move.
"The French Republic was not built on tolerance. And the Republic of Korea must straighten its national spirit by punishing criminals related to the insurrection," Jung added. "The DP will be at the forefront of the effort to eradicate the insurrection."
In a media scrum after the victory speech, Jung said he was not yet ready to work with the PPP.
"We're at war with the insurrection," he said. "Unless they apologize and express their remorse for destroying the Constitution and attempting to kill people, I will not shake hands with them." (Yonhap)
