South Korea is on the brink of major political upheaval following Yoon Seok-yeol’s declaration of martial law and subsequent impeachment. While there is a chance Yoon could be reinstated, his removal would pave the way for a new presidential election likely to be won by Lee Jae-myung. Lee’s sweeping parliamentary support could drive substantial domestic reforms, including implementing an unconditional basic income. Meanwhile, Donald Trump’s return to the White House complicates Seoul’s foreign policy, especially as Trump may seek to cut Seoul out of North Korea negotiations. If Yoon remains in office, political turmoil could deepen, though foreign relations may see less immediate disruption.
South Korea enters 2025 under its most uncertain outlook in recent memory. Domestically, it is mired in a rolling constitutional crisis sparked by then president Yoon Seok-yeol’s 3 December 2024 declaration of martial law. On foreign policy, Seoul now faces a US president in Donald Trump, who has voiced hostility toward South Korean alliance.
The resolution of the first factor, coupled with the management of the second, could radically shift South Korea’s position on a range of relationships in the region. First, the country must resolve the current leadership vacuum that continues to deepen its already severe political polarisation.
Domestically, nothing looms larger than Yoon’s impeachment trial. Yoon was officially impeached by the National Assembly on 14 December 2024 and his trial before the Constitutional Court — which will decide whether to uphold his removal from office or clear the way for his return — began on 14 January 2025.
By law, the Court has 180 days to reach a final verdict, but most expect a decision much sooner. Some guidance can be gleaned from the impeachment of former president Park Geun-hye by the National Assembly on 9 December 2016, Park faced formal hearings before the Constitutional Court beginning on 3 January 2017. She was officially removed from office on 10 March 2017.
A similar timeline seems to be unfolding for Yoon. While there is a chance that his impeachment could be overturned, restoring him to office, that seems unlikely. Instead, his removal by the Constitutional Court would start the clock for the country to hold its next presidential election within 60 days, likely in early May 2025.
But the parallels with Park’s ouster only go so far. At that time, Park’s own party joined the rest of the country in condemning her actions while president, speeding her removal. In Yoon’s case, his People Power Party has fractured, with the majority of its sitting representatives siding with the president and against broad public opinion that favours his impeachment. This will make virtually any candidate the party puts forward in a 2025 presidential election unelectable.
So long as he remains eligible to run, the early favourite to win the election is Lee Jae-myung, current leader of the progressive Democratic Party who lost the previous presidential election to Yoon. Assuming that he wins, Lee would be in position to reform the country drastically. His party and its coalition partners hold 192 of 300 seats, allowing them to push through virtually any policy they wish.
The policy agenda from Lee’s failed 2021 bid for president — which included an unconditional basic income, a tax on land and a carbon tax — can be dusted off and ushered through. But reforms to education, the pension and the health system are also desperately needed. The conservative PPP may be able to gum up the process by abusing its committee chair privileges but would otherwise be effectively powerless to stop these reforms. That helps explain why they continue to defend Yoon’s martial law declaration. And if the Democratic Party pushes forward, the PPP may resort to calls for violence directed at political rivals.
If Lee is elected as South Korea’s next president, it would neatly align his presidency with Trump’s second term. The foreign policy to-do list will be long. Lee will want to reorient relations with an unpredictable United States, rework relations with Japan, aim to reposition South Korea between China and the United States, and manage an always threatening North Korea. Still, the combination of Trump and Lee may work better than expected on some key points.
In office, Trump will likely push for South Korea to take more responsibility for its own security. This has been a goal shared by progressive presidents in the past. For example, the Moon Jae-in government sought to complete the transfer of wartime operational control by 2022 and oversaw the largest defence spending increases of any South Korean president. Lee will likely pick up where Moon left off in pursuit of wartime operational control, giving him a common understanding with Trump about South Korea’s future role within the alliance.
Even if Trump seeks to force a renegotiation of the Special Measures Agreement — which governs how much South Korea pays to cover the costs of hosting US troops — South Korea could head this off by announcing large purchases of US military hardware that also contribute to progress on wartime operational control.
Another agenda item for Trump will be trickier for whoever is South Korean president. Renewing diplomacy with North Korea will likely be a high priority for Trump, but that does not necessarily bode well for Seoul. Both Donald Trump and Kim Jong Un may prefer to cut South Korea out of those discussions. Positioning Seoul to ensure it has a seat at the table for a matter vital to domestic national security will be critical for any president.
With Lee as president, relations with Japan will take a significant step backwards. An important driver of the rapprochement with Japan during Yoon’s early years in office was pressure from the Biden administration. Not only will that pressure be missing, but Trump has provided no evidence that he thinks about the United States’s position in Asia in anything but bilateral terms. He is unlikely to care if South Korea and Japan are no longer getting along as well as they had in previous years.
For South Korea, the year ahead looks daunting. If Yoon is returned to office by the Constitutional Court, the challenges become even more daunting. Such a decision would likely set off massive protests, creating even more gridlock and uncertainty domestically, though it might smooth the immediate direction of South Korea’s foreign policy.
Karl Friedhoff
Karl Friedhoff is the Marshall M Bouton Fellow for Asia Studies at the Chicago Council on Global Affairs.