The outcome of South Korea’s parliamentary elections seems undeniable. The opposition Democratic Party (DP) won a convincing victory and together with its progressive allies will hold a commanding 192-seat majority in the 300 seat National Assembly. Former DP presidential candidate and current party leader Lee Jae-myung is cemented, for now, as the likely presidential standard bearer when the next election is held in three years.

President Yoon Suk-yeol now faces an invigorated opposition eager to challenge him on every front. The conservative People Power Party (PPP) is fractured and likely to descend into a battle for succession that may leave Yoon increasingly isolated within his own party.

While that much is fairly clear, what remains uncertain is whether Yoon’s ability to reshape South Korea’s foreign and security policy — the hallmark of his rule to date — can survive. The consensus among foreign observers is that given the extensive powers of the executive in South Korea’s political system and broad public support for the larger goals of Yoon’s policies, there will be no significant shift in South Korean foreign policy.

The opposition is poised to focus more on domestic matters, from investigations of wrongdoing by the First Lady and senior officials to addressing potent economic issues, in the belief that those will put the conservatives on the defensive and may even open the door to impeachment.

Yoon, meanwhile, has signalled that he sees no reason to change course. In his first speech after the election, the President’s message was that his policy direction was correct but that he failed to communicate or produce visible results, observes Benjamin Engel, a Research Professor at Seoul National University.

Yoon’s stubborn determination to stay the course is not new, but the election result demonstrates that this cannot overcome the powerful force of public opinion in South Korea’s highly polarised environment. While support for the US alliance remains overwhelming, there is a strong current of nationalism that often takes on an anti-US tint.

The DP and its close allies in the newly elected National Assembly now include open advocates of the withdrawal of US troops and even the end of the security alliance. These tend to overlap with pro-North Korean views, often expressed in the belief that the United States is the main obstacle to a return to engagement with Pyongyang. North Korea policy is certain to be an ongoing point of contention between the opposition and the Yoon administration.

The opposition also mirrors a broader criticism of what is characterised as an anti-China policy adopted under US pressure to the detriment of South Korea’s own economic and security interests. The downturn in South Korea’s exports to China and tensions over the United States’ push for limits on technology trade with China have already been tapped as a point of attack against Yoon.

‘China was South Korea’s top export market, but now South Korea is importing mostly from China’, Lee said during the National Assembly campaign. ‘Why do we care what happens to the Taiwan Strait? Shouldn’t we just take care of ourselves?’.

Yoon’s administration is already reluctant to embrace calls for confrontation with China, particularly in the economic realm. Seoul will reportedly host a resumption of the China–Japan–South Korea trilateral summit in May 2024.

But Yoon’s call for South Korea to be a ‘global pivotal state’ rests on a consolidated alliance with the United States, the elevation of ties with Japan and tightened trilateral security cooperation. All of this draws South Korea into a de facto China containment strategy.

The greatest point of vulnerability in Yoon’s foreign policy is the embrace of relations with Japan and the attempt to resolve historical wartime tensions through a unilateral move to offer compensation payments to former Korean forced laborers. Without agreement from Japan to allow payments from Japanese firms, who have been sued in South Korean courts, Yoon proposed using an existing South Korean fund.

But this has proven to be, as some predicted, a fragile solution — the fund lacks sufficient money and numerous cases continue to move through the courts. Opinion polls show a significant gap in perception between Japanese and South Korean people over the state of relations, driven largely by what South Koreans see as Japan’s failure to reflect on its past and promote reconciliation. This scepticism is shared in both progressive and conservative camps.

US and Japanese officials tend to brush aside these concerns, eager to claim the fruits of security cooperation and investment in Yoon’s personal leadership. But the election results now raise serious questions about the sustainability of this policy, argues Wi Sung-lac, a former senior Foreign Ministry official and newly elected member of the National Assembly.

‘I have long raised concerns about this situation with my Japanese and American friends,’ Ambassador Wi, a close advisor to the DP leader Lee, told this writer in an email exchange. He argued that the ‘Yoon administration should communicate more with the opposition to gather public support, Japan should respond with more flexibility, and the United States should be aware of this situation and place the necessary advice for Korea and Japan. However, many Japanese and American friends did not pay much attention because they believed that the issue had now been resolved.’

 In Wi’s view, shared by many in his party and in public commentary, the ‘huge defeat’ suffered by the ruling conservatives and by Yoon reopens the door. At the top of the list of unpopular policies is Korea–Japan history. The South Korean media is already filling with coverage of Japanese Prime Minister Fumio Kishida’s dispatch of offerings to the controversial Yasukuni shrine.

Yoon is doing his best to maintain momentum in the Japan relationship, as is Kishida. But both men are weakened, with support ratings stuck in the 20s or low 30s. If the Japan–South Korea relationship slips into contention, it will undermine not only the alliance with the United States, but also the ability to hold a tough line on North Korea.

Looming over all of this is the uncertainty of a possible return to power by Donald Trump, a known advocate of the withdrawal of US forces from South Korea. ‘If for whatever reason it looks like Trump is going to win’, says Engel, ‘that’s when Yoon starts to change his approach’.

Daniel Sneider is Lecturer of International Policy and East Asian Studies at Stanford University and a Non-Resident Distinguished Fellow at the Korea Economic Institute.