South Koreans are voting to elect a new president after enduring months of political turmoil sparked by former leader Yoon Suk Yeol's botched attempt to impose martial law last December.
Turnout is expected to be high with voting open for 14 hours until 8pm local time at 14,295 polling stations across the country.
Early voting on Thursday and Friday saw over a third of the 44.39 million eligible voters cast their ballots. By 7am local time on Tuesday, another 1.08 million voters, nearly 2.4 per cent of the electorate, had exercised their franchise, according to the National Election Commission.
“We were the first to arrive with the hope our candidate gets elected and because the presidential election is the most important," Yu Bun Dol, 80, told AFP news agency in Seoul.
The new leader will face the challenge of rallying a society scarred by the attempt at military rule and an export-heavy economy hit by tariffs by the US, a major trading partner and a security ally.
Lee Jae Myung of the liberal Democratic Party is favoured to win the election. A Gallup survey shows almost 49 per cent of South Koreans viewing him as the potential new leader.
Both Mr Lee and his conservative rival Kim Moon Soo propose to make major changes, arguing that the political system and economic model set up during its rise as a budding democracy and industrial power are no longer fit for purpose.
Though their proposals for investing in innovation and technology often overlap, Mr Lee advocates for more equity and help for mid-to-low-income families compared to Mr Kim's campaign for more freedom from regulations and labour strife.
Mr Lee has called the snap election "judgment day" against Mr Kim and his People Power Party, accusing them of having condoned Mr Yoon’s martial law attempt. The Democratic Party candidate has urged voters to rally behind his campaign theme of “overcoming insurrection".
In his final campaign speech, Mr Lee called Yeouido in Seoul a “historic site where the darkness of insurrection was driven out by the light of democracy".
“We will complete the revolution of light that began here in Yeouido," he was quoted as saying by The Chosun Daily.
Mr Kim has denounced his rival a "dictator" and his Democratic Party a "monster", warning that if the former human rights lawyer became president, he and his party would be left unconstrained to amend any laws they simply did not like.
The conservative nominee claimed he would “never deceive the people or mislead them with lies”. He pledged to revive the economy and create “a great Republic of Korea where integrity prevails, corruption is eradicated, and hardworking citizens are respected".
The snap election was called after South Korea’s Constitutional Court ousted Mr Yoon as president earlier this year for imposing martial law. Mr Yoon had been impeached by the National Assembly and the court upheld the parliamentary decision.
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