By Ju-min Park and David Chance
SEOUL (Reuters) - South Korea's December presidential election looks set to turn into a referendum on two of the country's most polarizing leaders as the daughter of military dictator Park Chung-hee faces off against a former aide to ex-President Roh Moo-hyun.
Park's authoritarian rule propelled South Korea from poverty to the cusp of developed-nation status and ended when he was assassinated in 1979. The left-wing Roh's single five-year term closed in chaos as economic reforms failed and a policy of engagement with North Korea was wrecked as Pyongyang pushed ahead with a nuclear weapons program.
Roh committed suicide in 2010 after bribery charges dogged his retirement.
The conservative candidate, Park Geun-hye, 60, who is bidding to become South Korea's first woman president, and left-winger Moon Jae-in, 59, formally registered their candidacies on Sunday after independent Ahn Cheol-soo dropped out to support Moon.
"It is going to be a negative election campaign," said Kim Jun-seok, a political science professor at Dongguk University in Seoul. "People will split between the 'pro-growth' generation that supports Park Chung-hee and the 'pro-distribution' generation that supports Roh Moo-hyun."
Initial polls showed Moon had a slight edge over Park as Ahn's supporters rallied behind a candidate who has pledged engagement with North Korea, to renegotiate a free trade agreement with the United States, to increase taxes on the wealthy and tackle the power of big business.
A survey from pollster Realmeter published on Saturday put Moon, who says his favorite political moniker is "Shadow of Roh", on 48.1 percent versus Park's 46.2 percent. Broadcaster MBC gave Moon 41.2 percent to Park's 39.2 percent.
The lead was within the margin of error and success for Moon will likely hinge on whether he and his Democrat United Party, which failed to oust the ruling conservatives in parliamentary polls in April, can win the support of Ahn supporters who wanted a break with South Korea's established political parties.
Polls showed that Ahn, a software mogul and philanthropist, had until recently been rated the candidate more able to beat Park and to galvanize the support of disenchanted young voters.
Analysts cautioned against reading too much into the polls which also showed that between a quarter and a third of Ahn supporters were now undecided.
"Despite the latest surveys showing Moon Jae-in has a slight lead, the two main players are running neck and neck in the race," said Kim Kwang-Dong, chief analyst at independent political think-tank the Nara Policy Institute.
In addition to Park and Moon, two fringe candidates have so far also registered.
CONFRONTATION POLITICS, CLASS WARFARE
Park, who disappeared from public life after the death of her father and re-emerged as a politician in 1997 when South Korea was plunged into the Asian financial crisis, has made two previous bids to win the conservative candidacy.
Fighting back tears at a press conference at which a flustered Park initially misspoke and said she would step down from the presidency, she formally registered her candidacy on Sunday and pledged an era of "national reconciliation".
"If I do not receive your confidence at the presidential election, I will be ending my political journey," she said.
Like Moon, Park has promised greater "economic democracy" and better social welfare, although she has stressed that the big family-run businesses that dominate South Korea - the so-called chaebol - are essential to the country's success and its ability to create jobs.
She has termed her father's coup as "unavoidable and the best possible choice". At the same time, she says she has always been "apologetic" to victims of her father's push for industrialization, when he suppressed dissent in the face of threats from North Korea.
Moon has refused to visit the grave of Park Chung-hee, who put him in prison, and says that his daughter enjoyed a life of luxury in the presidential mansion and cannot understand the difficulties of ordinary people.
"When I was living in poverty, she was living the life of a princess in the Blue House," Moon said when he declared his candidacy earlier this year. "When I was fighting against dictatorship, she was at the heart of it."
On Sunday, he returned to the theme, setting the stage for a bitter final few weeks of campaigning that political analysts said would likely turn off many uncommitted voters.
"Please choose the force that can safeguard people's welfare and livelihoods and square up to the forces that protect the chaebol and the privileged class," Moon said.
(Additional reporting by Jack Kim, Sung-won Shim and Somang Yang; Editing by Nick Macfie)