A court in South Korea condemned the opposition leader Lee Jae-myung for violating the electoral law, casting doubt on the prospects of him running for president in next year’s elections.

The Seoul Central District Court found that The leader of the Democratic Party is guilty of making a false claim about a land development project in 2021 while campaigning for the presidency.

The court gave him a one-year prison sentence, suspended for two years.

Lee, however, said he would appeal the decision to a higher court. “It’s a conclusion I cannot accept,” Lee told reporters as he left court.

“There are still two courts left in the real world, and the courts of public opinion and history are eternal,” he said, apparently referring to plans to take the case to the Supreme Court.

Lee is a liberal who lost the 2022 election to the conservative president Yoon Suk Yeol with a thin edge.

He has become a front-runner to unseat Mr. Yoon, whose approval ratings have fallen to record lows while he he is struggling with his own political scandal.

Lee’s chances increased after a landslide victory in April’s parliamentary election, and he won enough seats in parliament to put pressure on the conservative People’s Power Party.

Considered one of the most polarizing figures in South Korean politics, Lee, a former child factory worker who suffered an industrial accident after dropping out of school, has often highlighted his rags-to-riches journey to political stardom.

However, his career has been overshadowed by scandals and allegations of ties to organized crime.

In January, Lee survived a knife attack, suffering a neck injury that required surgery.

In 2022, prosecutors indicted Lee on charges of making false claims about two controversial development projects in Seongnam, where he served as mayor from 2010 to 2018, during his campaign as the Party’s presidential candidate Democratic.

On November 25, the same court will rule on another case against Lee, in which he is accused of perjury by pressuring a Seongnam City employee to testify falsely in another court case in 2019.

The testimony was intended to minimize his 2003 conviction that, while a lawyer, he helped a television journalist pose as a prosecutor to secure an interview with then-Seongnam Mayor Kim Byung-ryang in connection with the suspected of corruption in 2002.

Lee has denied any wrongdoing and accused the government of Mr. Yoon, a prosecutor turned president, of pursuing a political vendetta.

Additional reporting by agencies