SEOUL • For years, Mr Ahn Cheol Soo would rise at 3am, warming himself with a blanket and a cup of coffee, to code a computer anti-virus program that he would later distribute free to millions of South Koreans, making him a household name.
The company the 54-year-old founded in 1995, Ahnlab Inc, went on to become South Korea's leading anti-virus software developer.
On Thursday, its shares surged as much as 21 per cent after its biggest shareholder, who began dabbling in politics about five years ago, led his People's Party to a strong showing in parliamentary elections.
The party almost doubled its seats, denying President Park Geun Hye's party a majority and setting Mr Ahn up as a kingpin in the new legislature.
The poor showing by Ms Park's Saenuri party has raised the risk of further gridlock in Parliament and sets back her economic agenda.
Securing Mr Ahn's support will be key for her to be able to pass legislation in her final two years in office. So far, Mr Ahn has not indicated whether he will back her.
Mr Ahn's party landed 38 seats in the 300-member Parliament, giving him the potentially deciding vote on legislation.
Saenuri lost 24 seats to finish with 122, and the main opposition Minjoo Party squeaked ahead with 123.
Mr Ahn, a medical doctor, formed his party only in February after breaking off from the main opposition Minjoo Party to offer a more centrist alternative to the main political groupings. He was elected to Parliament in Wednesday's vote.
Professor Robert Kelly, a political science professor at South Korea's Pusan National University, said: "Young conservatives bolted Saenuri and they didn't want to vote for the Minjoo, because they think it's too left-wing and too pro-North Korea. They looked at Ahn like the centre-right alternative."
Mr Ahn almost ran in the 2012 presidential race, but opted to support another candidate.
With Ms Park limited to a single five-year term, his showing in the election leaves him well positioned to contest the presidency next year.
In a Realmeter poll released on Thursday, he trailed former Minjoo leader Moon Jae In as the most popular choice for president.