South Korea’s acting leader, Prime Minister Han Duck-soo, said Thursday he is resigning to take on “heavier responsibility” amid expectation he will run in next month’s presidential election.

Han has emerged as a potential conservative standard bearer as the main conservative People Power Party remains in disarray over the recent ouster of President Yoon Suk Yeol. Observers expect Han to officially launch his presidential campaign on Friday.

“I have two paths ahead of me. One is completing the heavy responsibility that I handle now. The other is putting down that responsibility and taking a heavier responsibility,” Han said in a nationally televised announcement. “I’ve finally determined to put down my post to do what I can and what I have to help overcome the crises facing us.”

Han, who Yoon had appointed prime minister, the country’s No. 2 post, is expected to align with the People Power Party to launch a unified conservative campaign against liberal front-runner Lee Jae-myung, observers say.

Han, 75, is a career bureaucrat with about 40 years of public service and a Harvard doctorate in economics. He has held many top posts under both conservative and liberal governments, including trade minister, finance minister and ambassador to the U.S. He’s served as prime minster twice, first under liberal President Roh Moo-hyun from 2007 to 2008 and later under Yoon.

Han’s supporters say his extensive government experience, especially on economic affairs, would make him the right leader who can deal with President Donald Trump’s aggressive tariff policies and other economic problems. But his critics say Han — who has never had an elected post — has no strong political support base and is too old to become president.

Lee’s main liberal opposition Democratic Party lambasted Han’s move. “Only the people’s severe punishment awaits Prime Minister Han Duck-soo, who is blind with greed and abandons state affairs,” party spokesperson Cho Seung-rae said.

Han is to formally end his term at midnight after he signs a related document, according to South Korean media. With Han’s resignation, Deputy Prime Minister Choi Sang-mok becomes acting president until a new leader is elected on June 3.

Lee, who won the nomination of the Democratic Party on Sunday, has been favored to win. But his campaign suffered a blow Thursday after the Supreme Court ordered a lower court to review its earlier cancellation of his conviction over election law violation charges.

While it’s unclear the Seoul High Court will come up with a new ruling on Lee before the June 3 election, the development provided his conservative rivals with fodder for a political offensive. Under South Korean law, anyone who receives a fine exceeding 1 million won ($683) for election law violations is barred from running for elections for five years.

The Democratic Party condemned the Supreme Court for allegedly trying to interfere in the election.

After the liberal opposition-controlled parliament impeached Yoon on Dec. 14 over his martial law declaration that plunged the country into turmoil, Han began serving as acting leader. But Han quickly clashed with Lee’s Democratic Party over his refusal to fill three vacant seats on the nine-member Constitutional Court, which was deliberating whether to formally dismiss or reinstate Yoon. A court decision to dismiss Yoon needed support from at least six justices.

In late December, the Democratic Party and other small opposition parties voted to impeach Han, accusing him of obstructing the restoration of the court’s full membership and abetting Yoon’s martial law decree. In March, however, the Constitutional Court overturned Han’s impeachment, reinstating him as acting president. The court in early April ruled to dismiss Yoon.

Yoon separately faces a criminal trial for rebellion in connection with his martial law decree. On Thursday, prosecutors added charges of abuse of power, according to a Seoul prosecutors’ office.