SEOUL South Korea is to hold a presidential election on May 9 to choose a successor to Park Geun-hye, who was removed from office in a historic court ruling last week over a widening corruption scandal.
Park's replacement will face a host of problems: a growing threat from nuclear-capable North Korea that has prompted deployment of a U.S. missile-defence system, Chinese retaliation against Korea businesses over that deployment, and pressure to reform the family-run conglomerates that played a key role in the scandal that caused Park's downfall.
Following is an introduction to the leading candidates and their positions on main issues.
The 64-year-old former lawmaker and ex-leader of the main opposition Democratic Party lost to Park in the 2012 election by 3 percentage points. Moon favours a delay in deployment of the U.S. THAAD missile defence system, saying the next government should make the final decision and parliament should approve it.
He has called for the need to "embrace and be united with" the people of North Korea, adding he could never accept its "dictatorial regime" or its trampling of rights.
He has also pledged to get tougher on the conglomerates, saying they need reform.
Moon has been at the top of polls, registering 32 percent in the latest one released by Gallup Korea on Friday. The polling company is not affiliated with U.S.-based Gallup Inc.
A youthful-looking An, 51, surged to second place in opinion polls after former U.N. chief Ban Ki-moon dropped out of the race. An was an aide to former President Roh Moo-hyun, a liberal, when Moon was Roh's chief of staff. He is a two-term governor of rural South Chungcheong province. Some supporters have nicknamed him the "Obama of South Korea".
An came second in the latest poll, with support of 17 percent of the 1,005 people questioned.
An also favours more engagement with North Korea but has said the THAAD deal should be respected as South Korea and the United States have agreed to deploy it. He has called for a fair, transparent market economy.
Ahn, 55, is a former doctor and computer businessman.
Ahn's popularity has waned in recent months after stepping down as co-chair of the new opposition People's Party after it became embroiled in a kickback scandal over advertising funds. Ahn was not implicated. He is a member of parliament.
He got the support of 9 percent of respondents in the latest poll.
He is open to dialogue on North Korea, though he has also advocated a tough line. He says the THAAD system must be deployed and South Korea must make greater efforts to convince China it is not aimed at them. On the economy, he advocates the expansion of small- and medium-sized enterprises.
Lee, the 52-year-old mayor of Seongnam, a city southeast of Seoul, has surged in opinion polls as an outspoken critic of Park since the scandal that led to her impeachment erupted.
A member of the main opposition Democratic Party, Lee has said he wants to be the South Korean Bernie Sanders, after the U.S. Democratic Party rebel who ran against Hillary Clinton.
He got the support of 8 percent in the latest poll.
Lee has billed himself as the inheritor of the "Sunshine policy" of engaging with North Korea. He recently told Chinese media the THAAD deployment should be called off. He is well known for his staunch criticism of the chaebol.
(Reporting by Ju-min Park; Editing by Robert Birsel)