SEOUL • Mr Ahn Cheol Soo has been a medical doctor, university professor, television host, tech entrepreneur and lawmaker.
Now 55, he is eyeing the country's top post as the candidate of the centre-left People's Party.
A relative newbie in politics, Mr Ahn promises a wave of "new politics" and brings hope to a country in need of bold reforms after the crushing impeachment of a scandal-hit president.
"I will be the first president to open up our future," he proclaims in a campaign advertisement.
But Mr Ahn, who shot to fame two decades ago as South Korea's Bill Gates after developing an anti-virus software program, has also drawn criticism for his lack of political experience and for changing his stance on North Korea to appeal to conservatives.
SEEKING TO MAKE COUNTRY BETTER
A student came to see me one day when I was teaching in university, and he shed tears while confiding his worries. I went into politics because I no longer wanted to see young Koreans cry. I made up my mind to do my part to make this country a better place.
MR AHN CHEOL SOO
His lacklustre performance in television debates, where he came across as inarticulate at worst, also caused his approval rating to plummet to half of front-runner rival Moon Jae In's.
Yonsei University political science professor Rhyu Sang Young describes Mr Ahn as a "very good politician" who pursues a moderate approach. "But his position is pinched between the progressive and conservative groups."
Opinion polls do not really matter to Mr Ahn, said his spokesman, Ms Nemo Kim. "He doesn't believe in them. He didn't look worried when his approval rating went below 10 per cent, and he didn't look happy when it was really high."
What Mr Ahn cares about is going the extra mile to reach out to voters, she said.
He has been making a splash online with a new strategy - to walk around the country and take the subway between rally points so as to talk to as many voters as possible in the last 120 hours of his campaign. The walk, captured live on Facebook, drew 2.84 million viewers last Thursday.
Born into a family of doctors, Mr Ahn studied medicine at the top Seoul National University but switched careers after developing anti-virus software in the late 1980s. The tech empire he built around it is now worth an estimated 100 billion won (S$123.7 million ).
Mr Ahn, who is married with a daughter, credits a former student for his foray into politics in 2011. Last year, he founded his People's Party, which won 40 out of 300 parliamentary seats in the April elections.
"A student came to see me one day when I was teaching in university, and he shed tears while confiding his worries," he said on Arirang TV. "I went into politics because I no longer wanted to see young Koreans cry. I made up my mind to do my part to make this country a better place."