SEOUL (Reuters) - A man who was once imprisoned by South Korea's former military dictator, Park Chung-hee, said on Sunday he would seek the centre-left's nomination to run for president, likely setting up a contest with the daughter of the man who jailed him.
Moon Jae-in, a former aide to ex-president Roh Moo-hyun, announced his bid for the presidency, seeking to unite the fractured left in a battle that is likely to pit the winner of the left's internal contest against Park Geun-hye, the ruling conservative party's candidate.
Moon, 59, had earlier worked in a law partnership with Roh, taking on human and civil rights cases.
Though a relative unknown on the national stage, he is the centre-left's front runner in opinion polls, with support ratings of around 12 percent. He hopes to capitalize on unease over growing income gaps between rich and poor in South Korea, the world's 13th largest economy.
Moon was jailed in 1975 for joining street protests against Park's father, Park Chung-hee, whose 18 years in power were marked by both rapid economic growth and crackdowns on dissent. At that time, Park served as first lady after her mother was assassinated by a pro-North Korea militant.
He lies some 30 percentage points behind Park, 60, the clear front-runner in the polls to be held in December.
"Our society does not share the wealth of economic growth anymore," Moon told 2,000 supporters in a park near the prison he was sent to in 1975.
"A small number of rich people and large conglomerates have warehouses that are full of gold, but most ordinary people go to bed every day fretting over employment, housing, jobs, health and old age."
The centre-left had looked set to oust the conservative Saenuri Party in parliamentary elections in April, but stumbled and the scandal-tainted ruling party held on to its parliamentary majority.
Commentators gave Park, a quietly spoken and slight woman dubbed "The Queen of Elections", credit for rescuing the conservatives.
Moon had stayed out of the political limelight until the suicide of former president Roh in 2009 over corruption charges.
He complains that conservative President Lee Myung-bak has presided over growing income inequality as his mandatory single term of five years draws to a close.
Moon also engineered closer relations with North Korea, setting up a summit between Roh and then-North Korean leader Kim Jong-il in 2007.
Relations on the Korean peninsula have soured since Lee took office and Kim Jong-un, who took office in December, has adhered to his late father's hardline "military first" policies.
"Other than the fact that he was Roh's chief of staff, his name or leadership is barely known," said Ka Sang-joon, a political science professor of Dankook University.
"Being less well-known could be strength for Moon because people can hope he could be someone new and different but it can also be a risk once he gets out into the spotlight."
Moon is the second left of centre politician to announce his candidacy. While he faces relatively weak challengers from within his own Democrats party, he could come under pressure to stand down if popular software mogul and philanthropist Ahn Cheol-soo decides to run.
Ahn almost matches Park in opinion polls but has not formally said he will stand. If he does contest the election, it will be as an independent.
Reporting by Ju-min Park; Editing by David Chance and Ron Popeski