South Korea's Democratic Party presidential candidate Lee Jae-myung maintained a significant lead in opinion polls on Monday, though his eligibility to run rests on the outcome of legal trials over election law violations.

In a survey conducted by Realmeter of 1,505 adults aged over 18 on April 23-25, Lee led with 48.5 percent, despite a drop of 1.7 percentage points from last week.

"Lee Jae-myung's supporting rate fell slightly below the 50 percent mark due to concerns about uncertainty in judicial rulings on his case related to the election law violation," the pollster said in a report.

South Korea is set to hold a presidential election on June 3 after former president Yoon Suk-yeol was removed from office earlier this month over his Dec 3 martial law declaration.

Lee secured the nomination as his party's presidential candidate on Sunday with 89.77 percent of the vote. This marked the highest approval in Democratic Party-affiliated primaries since the country's democratization in 1987.

However, Lee is facing multiple criminal trials, including on corruption charges and violation of election law, in which guilty verdicts could render him ineligible to run for president for a decade.

If he wins the presidency before the verdicts are announced, he can claim presidential immunity and the trials will be suspended.

The lawyer-turned-politician lost the 2022 presidential election to Yoon by just 0.73 percentage points.

Besides Lee, former employment and labor minister Kim Moon-soo of the ruling People Power Party, or PPP, recorded a 13.4 percent support rate, according to Realmeter.

In his first official event as the party nominee, Lee visited the Seoul National Cemetery on Monday to pay respects to late presidents, including conservative presidents Rhee Syng-man and Park Chung-hee.

The visit was seen to broaden his appeal toward centrist and conservative voters, Yonhap News Agency commented.

After the visit, Lee told a party supreme council meeting that it is important to keep the community united and it is the president's job to lead the people toward one path, to maximize the energy and capabilities of the people and go beyond differences.

"Presidential candidates will have to go this way as well because the country is so torn right now," he said.

However, the PPP criticized the Democratic Party, saying the nearly 90 percent approval for Lee in the primary raised concerns over his party's "exclusion politics".

PPP spokesman Kwon Dongwook said on Monday that the Democratic Party has used its majority to deal with bills in the National Assembly and impeach cabinet members numerous times, going against Lee's stressing of unity.

Kim Jae-yeon, a candidate of the minor Progressive Party, said Lee's visit to the national cemetery cannot be seen as an act that helps national unity, as true unity must start with efforts to overcome minor differences among citizens who fought to defend democracy.

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