Lee Jae-myung – Changing Northeast Asian Security?

Why South Korea’s 2025 Presidential Election Could Reshape Northeast Asian Security

South Korea heads toward its next presidential election, and the stakes could not be higher — not only for its own citizens, but for the broader region of Northeast Asia. With further tensions flaring between North and South Korea, simmering disputes between China and Taiwan, the outcome of South Korea’s next election may well shape the trajectory of peace or conflict in one of the world’s most volatile geopolitical regions.

From Martial Law to Impeachment: Yoon’s Fall 

Yoon Suk Yeol was South Korea’s president. Following a declaration of martial law on the night of 3rd to 4th December on the grounds that the opposition in the South Korean Assembly was a threat to democracy and national security, he was stripped off his office and the Constitutional Court finalized his impeachment on April 4th, 2025. 

Since then, the political climate in South Korea has grown polarized, with the acting president Han Duck-soo also impeached by the opposition but reinstated by the Supreme Court. As Yoon has now been impeached, presidential elections need to be held in June 2024. For the presidential election, several Korean politicians have already announced to join the very intense presidential campaign. The new president of South Korea will play a crucial role in shaping South Korea’s foreign and security policy. Depending on the election results, his political agenda will decide if the country remains to have strong ties with the U.S. and Japan as in Yoon’s tenure or if South Korea tilts towards a more China-friendly stance and seeks to mend ties with North Korean dictator Kim Jong-un. 

Lee Jae-myung’s Comeback: A Foreign Policy Shift in the Making? 

The leading candidate for the 2025 presidential election is Lee Jae-myung from the Democratic Party of Korea. The former governor of the Gyeonggi Province enters the race for a second time after having lost very narrowly to Yoon back in 2022. As of April 20th, 2025, Lee is leading in an opinion poll with 48,8 percent. Therefore, Lee Jae-myung is the candidate who will most likely win the race for this office.

However, his candidacy is still uncertain. Lee remains the most promising contender if his appeal against the one-year sentence imposed on him in November 2024 is successful. If the Korean Supreme Court rejects the appeal, Lee would not be allowed to run for public office for ten years. The possible election of Lee Jae-myung as South Korean president would likely be another turnaround in South Korean foreign policy. Whereas trilateral relations between South Korea, the U.S. and Japan for example were improved during Yoon’s tenure, Lee is expected to lead South Korea away from Japan and the U.S. in the course of his term of office as it did in the time when Moon Jae-in was president and turn its attention back to North Korea and China as part of a new sunshine policy. The sunshine policy aims to actively seek cooperation with North Korea.

Furthermore, Lee has shown himself to be “anti-Japan” and has made negative comments about Japan in recent years. For example, he described Japan as a hostile nation and emphasised that Japan must be viewed critically due to its imperial past. He also questioned the focus on reconciliation between the two countries. Therefore, Japan fears a setback in the relations which have developed for the better during Yoon’s term. 

China Watches Closely: A Strategic Opening in Northeast Asia?

In the first impeachment motion, the opposition party around Lee criticized Yoon for antagonizing China and North Korea which eventually caused South Korea to be isolated together with Japan in the region. Lee further criticized that Yoon has risked a war and therefore endangered regional security. 

As president, Lee would likely advance with a left-leaning foreign policy view, which in South Korea usually result in a conciliatory stance towards China and North Korea as seen during Kim Dae-jung’s tenure from 1998 to 2003 and Moon Jae-in’s tenure from 2017 to 2022. This usually has caused tension in the relations with the United States. Lee is convinced that South Korea cannot afford to be on hostile terms with China and that the new government needs to find a balance between strengthening the security alliance with the U.S. while also stepping back from the front lines of the challenging geopolitical landscape in Northeast Asia. 

Not Just a Vote—A Geopolitical Turning Point?

The trilateral relation between the U.S., Japan and South Korea has long functioned as a counterweight to China’s political influence in Northeast Asia. If South Korea under a President Lee pivots away from this close alignment with Washington and Tokyo, it would result in visible cracks in the regional security architecture. A weakened trilateral cooperation between the U.S., Japan and South Korea allows China to act more offensive in the region and further push for a unification with Taiwan. With South Korea potentially stepping back from coordinated defence initiatives and joint military exercises, Beijing may feel emboldened to test the resolve of the remaining alliance structure. This could include increased military activity around the Taiwan Strait or grey-zone operations designed to wear down Taiwanese resistance and international support. In this scenario, the erosion of trilateral unity could accelerate a broader strategic shift, tilting the regional balance of power in China’s favour and heightening the risk of an armed confrontation between China and Taiwan in Northeast Asia.

With Lee Jae-myung leading the race, a potential shift in diplomatic posture is probable, provided his legal obstacles are cleared. His presidency could result in improved relations with North Korea and a recalibration of ties with China, likely at the cost of tensions with traditional allies. Therefore, this election is not merely a domestic event - it is a strategic turning point in Northeast Asia.