Former human rights lawyer Moon Jae In is poised to become South Korea's new president in a landslide victory, after his closest rivals conceded defeat yesterday.
Mr Moon, 64, of the liberal Democratic Party, won 41.4 per cent of votes in exit polls conducted by the country's top three broadcasters.
He was followed by Mr Hong Joon Pyo of the conservative Liberty Korea Party with 23.3 per cent, and Mr Ahn Cheol Soo of the centre-left People's Party with 21.8 per cent.
Official results will be announced only this morning by the National Election Commission (NEC), and the new president will take office immediately.
Mr Moon last night declared his victory, saying he will be a president for all South Koreans.
"I will build a new nation. I will make a great Korea, a proud Korea. And I will be the proud president of such a proud nation," he told supporters in Seoul's Gwanghwamun.
Voter turnout was 77.2 per cent, according to the NEC.
South Koreans went to the polls from 6am (5am Singapore time) yesterday, eager to pick a replacement for the disgraced Park Geun Hye, who was impeached in March over a corruption and influence-peddling scandal.
The election came after months of political turmoil over the scandal, which triggered massive candlelight protests. Park has been arrested and will face charges including extortion and abuse of power.
Her downfall fuelled resentment against the country's traditional elite and turned voters towards Mr Moon, who lost the 2012 presidential election to Park by 48 per cent to 51.6 per cent.
A win by Mr Moon this time would mark the end of nine years of conservative rule and a likely return to the Pyongyang-friendly policies of the former Roh Moo Hyun administration.
Mr Moon, who was chief of staff for the late Mr Roh, has pledged a two-track approach using dialogue and sanctions to resolve the North Korean nuclear issue.
He has also pledged to implement reforms to revitalise the economy and create jobs for young people, as well as reform the political system and cut off the cosy ties between conglomerates and the ruling elite.
Dr James Kim, a research fellow at the Asan Institute for Policy Studies in Seoul, said Mr Moon's popularity had surged after Park's scandal broke, and he kept up his approval rating with a careful and well-organised campaign.
Dr Kim said Mr Moon was consistent in his pledges though he made some adjustments to pander to the moderates after winning the party's primary last month. For instance, he had toughened his stance on North Korea.
Ms Gaye Kim, 28, who works at an Internet firm, voted for Mr Moon because she felt "he has a solid plan for the future".
Another of his supporters, housewife Ko Hyun Mi, 46, said: "I believe Moon Jae In is the kind of president who will keep his promises. I hope he will use his power to improve the economy and help Korean people."