SEOUL, May 8 (Xinhua) -- South Korea is set to hold a presidential by-election Tuesday as former President Park Geun-hye was impeached and arrested in March over corruption allegations.

Public demand for the transfer of presidential power exploded with the influence-peddling scandal, involving Park and her longtime confidante Choi Soon-sil who is also now in custody and on trial for bribery charges.

Voters demanded the severing of cozy ties between conglomerates and politicians, calling for the narrower gap in income inequality and more jobs for youths.

Security issues emerged as a key talking point during the campaign period as tensions escalated on the Korean Peninsula for the dispatch of a U.S. aircraft carrier to the region and the subsequent belligerent rhetoric from the Dedsmocratic People's Republic of Korea (DPRK).

Following are major presidential candidates of South Korea for the upcoming election and their positions on main issues:

Moon Jae-in, 64, is a presidential candidate of the biggest Minjoo Party, leading the latest polls by a wide margin.

His support scores began to rise when the corruption scandal embroiling Park emerged in October last year. The support rate had hovered around 40 percent, touching 38 percent in the first week of May, according to a weekly survey by Gallup Korea.

It almost doubled 20 percent garnered by his main rival, Ahn Cheol-soo of the centrist People's Party. Under the election law, no polls conducted after last Tuesday can be published before the election.

Moon was a student activist in the 1970s and was jailed for opposing the military dictatorship of former President Park Chung-hee, the father of the impeached Park.

Since 1980s, he had worked as a human rights lawyer together with late liberal President Roh Moo-hyun. When Roh became president in 2003, Moon served as his chief of staff and senior presidential secretary for civil affairs.

Moon ran for president in 2012, but he lost narrowly to Park by 51.6 percent to 48.0 percent. Since then, he has been attacked by conservatives as he remained a powerful presidential hopeful in the opposition bloc.

He advocated a more balanced diplomatic position between the United States and China, though he considered the U.S.-South Korea alliance as the most significant for defending against threats from the Democratic People's Republic of Korea (DPRK).

Moon is expected to champion, or inherit, the "sunshine policy" of taking a rapprochement approach to the DPRK through economic cooperation and personnel exchanges. It was advocated by Roh and his predecessor President Kim Dae-jung.

With the impeachment of Park, Moon promised to reform conglomerates, fight income inequality, expand social welfare systems and create jobs for youths, which liken their country as a hell amid the super-high unemployment rate for them.

Ahn Cheol-soo, 55, is a presidential candidate of the centrist People's Party that splintered away from the Minjoo Party in early 2016.

His support rate came closer to Moon's for the first two weeks of April, but it dropped to 20 percent in early May for voters' disappointment at his ambiguous stance on security issues and negative campaigning toward Moon as seen in TV debates.

The obscure stance was viewed as a strategy to gain conservative votes, but it seemingly resulted in both liberal and conservative voters turning their backs away from the centrist.

He was a medical doctor by training and turned into an entrepreneur who developed antivirus computer software.

In the 2012 presidential election, Ahn emerged as the most powerful rival to the impeached Park under the one-on-one race, but he withdrew his presidency not to split liberal votes. Ahn threw his support behind Moon.

Ahn advocated a so-called "Fourth Industrial Revolution" as the country's new growth engine by converging high technologies, but it was criticized by some of liberals as lacking the consideration of human beings.

Hong Joon-pyo, 62, is a presidential candidate of the former ruling Liberty Korea Party, with which the impeached Park was affiliated.

His approval rating stayed below 10 percent till the third week of April, but it began to rise in the next week and came closer to Ahn's by gaining 16 percent in the first week of May.

During the TV debates, Hong showed his hardline foreign and security policies, criticizing four other major rivals with offensive words.

His behavior was harshly slammed by liberals, but it successfully re-collected support from elder rightists despite the downfall of the conservative bloc following Park's impeachment.

Describing himself as "a strong man," Hong promised to crack down on what he called "belligerent, aristocratic unionists" if he is elected. He cited the labor unions as a key reason for the current economic slump.

Hong is a former prosecutor who was once famous for his thorough investigation into crimes "without sanctuary."

He is a four-term lawmaker and former governor of South Gyeongsang province, a former political home turf for conservative politicians.