The Peninsula

Lee Jae-myung's Centrist Pivot and the Future of U.S.–South Korea Alignment

After months of political uncertainty, South Korea has a new president. Lee Jae-myung, the former mayor of a wealthy Seoul satellite city who leveraged that experience into a governorship of the country’s most populous province and chairmanship of the Democratic Party (DP), won a decisive 49.4-percent victory over the ruling party’s leading candidate.

Lee’s victory was widely expected. He held a double-digit lead for most of the 2025 campaign and led the DP to a near supermajority in last year’s parliamentary elections. All this after losing the closest presidential election in South Korean history in 2022. Lee can attribute his success over the last three years to political acumen, his predecessor’s unpopular policies, and, most recently, his lurch toward the political center at a time when South Korean voters crave stability. Together, Lee made impressive inroads across the country in an election that saw the highest turnout in nearly three decades.

In other words, voters have given the progressive-turned-pragmatic centrist a clear mandate. Together with the DP-controlled National Assembly, President Lee has significant political capital and resources to pursue the industrial diversification and economic growth initiatives he so emphasized on the campaign trail. But his foreign and national security policies will receive the most scrutiny in Washington, and it’s here that Lee may have to work hardest to convince South Korea’s allies and partners that his new-look centrism is a permanent change. There will be similar dubiousness in Tokyo, as well as at least some UN Sending States heavily invested in the Western-aligned security architecture on the Korean Peninsula.

There are three factors at play here. First, like most Korean progressives, President Lee has a long track record of emphasizing engagement with North Korea. Campaigning for president in 2022, he praised then President Moon Jae-in’s inter-Korean policies and said they would serve as the blueprint for his own. He specifically called for UN sanctions exemptions and restarting now-long-dormant inter-Korean economic projects, likely including the Kaesong Industrial Zone and tourism at Mount Kumgang. The DP has previously criticized joint U.S.-South Korea military activity as unhelpful, and more recently, the DP-majority National Assembly submitted an initial impeachment motion against Yoon Suk Yeol that accused him of “antagonizing” North Korea.

Candidate Lee, however, has emphasized deterrence as the primary mechanism to respond to North Korean provocations, echoing language typically associated with the South Korean right. Voters in the country are more skeptical than ever about unification, and while North Korea does not typically move the needle in elections, emphasizing the West’s status-quo position on North Korea—deterrence first, other options secondary or not at all—is an increasingly uncontroversial position in Seoul and elsewhere. But U.S. President Donald Trump and then President Moon Jae-in were, perhaps surprisingly, mostly aligned on the merits of engagement with Pyongyang from 2018 onward. This, along with Lee’s historical track record, suggests that the United States and South Korea may find common ground once again if and when North Korean leader Kim Jong Un opts to open up again to dialogue and engagement.

The second and closely connected foreign policy area that Lee will have to build confidence around is the U.S.-South Korea alliance. Although the alliance and the United States itself remain overwhelmingly popular among the South Korean public, President Lee has previously referred to U.S. forces based in South Korea as an “occupying force,” an extreme interpretation of the otherwise conventional South Korean left’s position that while the U.S.-South Korea alliance is an important component of South Korean foreign policy, it may also constrain South Korean autonomy and limit its ability to pursue independent national interests. In the past, Lee also called for canceling the Terminal High Altitude Area Defense (THAAD) system, a U.S. ballistic missile deterrence technology based in South Korea’s southeast that became a polarizing issue after China retaliated against its deployment in 2017. But as candidate and now president, Lee is far more sanguine about the U.S.-South Korea partnership, calling the alliance the “foundation” of South Korean diplomacy and assessing the alliance positively in his inauguration speech. Here again, though, Lee’s more orthodox views from the left may find overlap with President Trump, who confined the scope and scale of U.S.-South Korea joint military activity during his first term and referred to routine drills as “provocations.” Beyond the executive offices in both countries, however, the military alliance between the two countries is so institutionally ingrained in the relationship that both Lee and Trump will encounter friction if either seeks to pirouette around it.

A third foreign policy area that President Lee faces incredulity about is whether the South Korea-Japan relationship will continue to improve under his administration. The 2023 Camp David Agreement sought to normalize an unprecedented level of military and nonmilitary cooperation between the United States, South Korea, and Japan in order to respond to advancing North Korean weapons of mass destruction and missile technology and growing regional threats. But Japan remains unpopular in South Korea, particularly among the political left, which successfully channels these sentiments into their political platform and messaging.

For example, the same articles of impeachment referenced above cite Yoon’s “strange Japan-centered” foreign policy as part of the rationale for removing him from office. Although the motion that ultimately passed did not include such language, this description tracks closely with the DP’s criticism of the former president’s efforts to improve relations with Japan since 2022. In October of that year, Lee Jae-myung suggested any form of military cooperation with the Japan Self-Defense Forces could lead to “the Red Sun flag” flying on the Korean Peninsula, a direct reference to South Korea’s colonial occupation by Imperial Japan between 1910 and 1945. Lee has even gone as far as to blame the United States for Japanese colonization and, as recently as 2023, said he still supports greater reparations for victims of colonial oppression, a cause that Moon pursued as well—much to the detriment of Seoul-Tokyo ties. Trilateral cooperation with the United States and Japan necessarily encourages coordinated “North Korea-China-Russia” aggression, Lee has previously stated, which may force South Korea to pick a side between the United States and China—something Lee has warned he does not want for the country.

But on the campaign trail, Lee was more centered. “We need to build South Korea-US-Japan cooperation” on top of the bilateral relationship with the United States, he stated in May. In February, he told the press that he has “no objection“ to Japan strengthening its military and reportedly reached out to Japan late last year to assuage concerns about continuity between the Yoon administration and his own. The current Trump administration’s commitment to the Camp David accords is unclear. But both South Korea and Japan may be able to convince the United States to stick to it if they emphasize the ways in which the agreement lessens the burden on the United States to coordinate between two critical allies against shared national security threats.

Lee Jae-myung’s presidential victory marks more than just a political comeback—it signals a potential recalibration of South Korean foreign policy. His transformation from progressive firebrand to pragmatic centrist gave him the mandate to lead a nation craving stability, and his party’s legislative strength grants him the tools to act decisively. But South Korea’s friends and neighbors are watching not just what Lee says but whether he governs as the centrist he campaigned to be. His challenge will be maintaining credibility at home while reassuring skeptical allies abroad—especially the United States and Japan—that his pivot is both genuine and lasting.

 

Arius Derr is Director of Communications at the Korea Economic Institute of America (KEI) in Washington, DC.

A version of this article first appeared on East Asia Forum.

Photo courtesy of the South Korean government via Flickr.

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