If Moon’s win is confirmed, he’s expected to reshape Seoul’s policy on North Korea, by challenging the deployment of the US missile defense system, THAAD, and opening talks with Pyongyang.
As counting gets underway, the exit poll showed Moon in first place with 41.4% of the vote, followed by conservative candidate Hong Jun-pyo at 23.3% and centrist Ahn Cheol-soo with 21.8%.
The exit poll does not include the more than 25% of South Koreans who voted early.
Voters were seeking to fill the void left by the impeachment of former President Park Geun-hye, who was ejected from office in March after a corruption scandal for which she’s awaiting trial.
Moon’s two closest rivals, Hong of the Liberty Korea Party and Ahn of the People’s Party, touted much tougher lines on North Korea.
Ahead of the vote, Pyongyang made its choice for South Korean president clear in a series of state media editorials calling for a boycott of conservative parties.
With former President Park, US President Donald Trump would have had a partner willing to take a hard line on Pyongyang. But Moon is seen as a candidate who could shake up the status quo in Seoul.
Quarter of South Korea already voted
South Koreans were faced with a daunting list of 15 candidates, however before polling day two had already dropped out of the race. Ballots are marked with a red stamp against the name of the selected leader.
More than 11 million people — about 26% of the electorate — participated in early voting, according to the national election committee. At the close of polling, an estimated 75% of South Koreans had cast their votes, according to the National Election Commission, though that figure is expected to change.
Many voters said they’re angry at Park and are ready for transparency. “The electorate wants to punish the whole party for the misrule of the Park era,” said John Delury, a professor at Yonsei University.
‘Tragedy will be extended’
North Korean state media took a shot at the departing conservative government the day before the vote.
“The tragic North and South Korean relationship had been brought on by the conservative groups, which have been in power for the past 10 years.
“They revived the period of confrontation and maximized the political and military confrontation,” the commentary in the state-run Rodong Sinmun newspaper read.
“If the conservative clique is to come into power again, the tragedy will be extended,” read the piece, which was credited to a personal contributor named Shim Chol Yong.
Some analysts say North Korea has toned down its provocations toward the South ahead of the election to avoid emboldening the country’s hard-liners.
What voters wanted
Despite the global focus on North Korea, the biggest priorities for South Koreans were the economy and corruption.
“We saw recently a slightly bad side of our government,” said college student Nam Woo-hyu, 26. He said the most important issues for him in the election were “the job market for young people and economic development.”
Although she is too weak to walk, 87-year-old Lim Sung-ryeom said she wanted to vote because she was “very concerned” about her country.
“It was a very tough day for me to come all the way to the polling station. But I cannot miss my chance of making a great country,” she told CNN.
When questioned, older voters said they were concerned about the prospect of a liberal leader such as Moon Jae-in coming to power.
Yoon Ji-na, mother to a 18-month-old daughter, told CNN after casting a vote that she came to the polling station in the hope that her vote would help the nation return to normal.
“I don’t have high hopes. But things cannot go worse, right?”
CNN’s James Griffiths, Ben Westcott and K.J. Kwon contributed to this report