Who will win the 2026 Seoul mayoral election?

The Democratic Party's Seoul mayoral primary blended public opinion polls. The Democratic Party of Korea's internal primary rules for the Seoul mayoral election integrated public opinion polls, which proved to be a point of contention among candidates ^[3]. Although the exact ratio of party member votes to public opinion polls for determining the nominee remains unspecified in available sources, the selection process initially involved a large field that was subsequently narrowed to three individuals ^[4]. Ultimately, Jeong Won-o, also known as Chong Won-o, successfully secured the party's nomination for Seoul mayor ^[1].

Park Ju-min advanced but was eliminated in the main primary. Regarding specific contenders, Park Ju-min advanced through preliminary stages but was eventually eliminated in the main primary ^[2]. Neither Seo Young-kyo nor Kim Min-seok are identified in the provided sources as participants in the final stages of the primary. A public opinion poll dispute involving Jeong Won-o and Park Ju-min occurred during the primary ^[3], which suggests the significant role these polls played in the overall selection process.

Jeong Won-o's nomination suggests favorability within the polling framework. His successful nomination, despite the dispute over public opinion polls, indicates that his candidacy was more favored within the overall framework that incorporated public opinion polling. It is not possible to definitively state which of the mentioned candidates would have been most favored by party loyalist votes versus general public electability without specific data on the individual weightings beyond the final outcome for Park Ju-min.

Han River Belt districts are pivotal due to real estate policy significance. The Han River Belt districts, encompassing areas like Yongsan-gu, Mapo-gu, and Seongdong-gu, are considered crucial swing areas where voter sentiment on real estate and urban redevelopment policies significantly influences election outcomes ^[2]. Notably, 'real estate stabilization and urban redevelopment' is the most critical issue for 38.2% of respondents in these districts when considering the upcoming mayoral election ^[1].

Mayor Oh's administration prioritizes extensive urban development and deregulation. Incumbent Mayor Oh Se-hoon's administration has focused on large-scale urban development and revitalization through initiatives like 'Seoul Vision 2030', advocating for accelerated reconstruction, redevelopment projects, and market deregulation ^[3].

Oh Se-hoon faces significant challenges, trailing opponents in key polls. Despite his administration's focus on these policies, Oh Se-hoon's overall approval ratings in these critical Han River Belt areas suggest he is generally trailing his main opponents ^[2]. A recent survey from April 22-23 indicated Oh Se-hoon with 33.6% support against Jung Won-oh's 44.9% in a hypothetical two-way race for Seoul Mayor ^[1]. Specifically within Seongdong-gu, a district with significant real estate development issues, Oh Se-hoon garnered 30.9% support, notably behind Jung Won-oh's 49.5% ^[4]. Voter sentiment regarding real estate and redevelopment policies in these key districts remains highly divided ^[5].

Over the last five Seoul mayoral elections, the incumbent party's candidate generally loses when presidential approval dips below 40%. Specifically, in the one instance within these elections where the president's nationwide approval rating fell below 40% in the quarter preceding the election, the incumbent party's candidate did not win. This strong correlation between presidential popularity and local election outcomes is evident in the 2021 Seoul mayoral by-election, where President Moon Jae-in's approval rating was recorded at 32% on April 2, 2021, and 33.4% on April 12, 2021, both below the 40% threshold before the April 7 election ^[2]. Consequently, the incumbent Democratic Party's candidate, Park Young-sun, lost to Oh Se-hoon of the opposition People Power Party ^[1].

Conversely, higher presidential approval often correlates with incumbent party victories in Seoul mayoral elections. Incumbent candidates generally performed better in elections where presidential approval remained above 40%. For example, in the 2018 Seoul mayoral election, the incumbent Democratic Party candidate won during a period of high approval for President Moon Jae-in ^[1]. Similarly, the 2010 Seoul mayoral election saw President Lee Myung-bak's approval rating exceed 50%, leading to the incumbent Grand National Party candidate securing re-election ^[3]. While the 2014 Seoul mayoral election resulted in an incumbent loss, President Park Geun-hye's approval rating, despite declining, did not fall below the 40% mark in the quarter leading up to the election ^[4].

The People Power Party (PPP) faces internal division between pro-Yoon and reformist factions. Within its Seoul party chapters, a "conservative rift" exists between pro-Yoon and non-Yoon factions ^[4]. While "pro-Yoon figures" demonstrate significant organizational strength by generating "backlash" against party leadership and those who criticize President Yoon Suk-yeol ^[1], the party is also making efforts to "distance itself from Yoon" ahead of local elections ^[4]. The confirmed PPP Seoul mayoral candidate, incumbent Mayor Oh Se-hoon, aligns with the "non-Yoon" or reformist wing, as evidenced by his demand for "party reform" when filing for his nomination ^[5]. This indicates that the "non-Yoon" faction, focused on electoral viability through reform and distancing from the president, currently holds sway in shaping the mayoral campaign strategy and candidate selection for the Seoul chapters, despite the pro-Yoon faction's strong presence.

The Democratic Party of Korea (DPK) exhibits strong unity behind its pro-Lee candidate. The DPK is demonstrating superior organizational strength and unity within its Seoul party chapters. The party's confirmed Seoul mayoral candidate is Jeong Won-oh ^[6], who is closely aligned with the "pro-Lee Jae-myung" faction, explicitly described as the "''Mild Lee Jae Myung'''" ^[3]. After securing the party's nomination, Jeong Won-oh successfully formed a "''One Team'' strategy" with his rivals ^[7], and DPK metro candidates have united behind this approach ^[2]. This cohesive strategy confirms that the "pro-Lee Jae-myung" faction is dominant within the DPK's Seoul chapters, effectively consolidating support and organizational efforts behind their aligned candidate without public indications of internal fundraising or organizational struggles akin to those observed in the PPP.

The People Power Party (PPP) established its Seoul mayoral primary timeline. Incumbent Seoul Mayor Oh Se-hoon officially registered his candidacy for the 2026 local elections on March 17, 2026 ^[1]. The party subsequently narrowed its Seoul mayoral contenders to three by March 23, 2026, including Oh Se-hoon, Park Sumin, and Yoon Heesook ^[4]. A significant event in their primary calendar was the first televised debate for the main primary, which occurred on March 30, 2026, where candidates discussed key issues such as real estate and transportation ^[5].

The Democratic Party also completed its candidate selection process for the mayoral race. The Democratic Party (DP) advanced Park Joo-min, Jung Won-oh, and Jeon Hyeon-hui in its Seoul mayoral primary on March 23, 2026 ^[6]. Jung Won-oh was ultimately confirmed as the party's Seoul mayoral candidate on April 6, 2026, after securing a majority vote in the main primary ^[2]. Following the selection of both major party candidates, a televised debate took place between Jung Won-oh and Oh Se-hoon, during which they engaged in "focused containment" ^[7]. The 2026 South Korean local elections, which include the Seoul mayoral race, are officially scheduled for June 3, 2026 ^[3].