South Korea's ruling Democratic Party (DP) swept the 4 June 2025 local elections and parliamentary by-elections, capturing 12 of 16 key mayoral and gubernatorial seats including the conservative stronghold of Busan, even as the opposition People Power Party (PPP) held on to Seoul with incumbent Mayor Oh Se-hoon winning a fifth term. The result, delivered exactly a year after President Lee Jae-myung took office, is being read as a powerful endorsement of his reform agenda.

Key results across regions

According to the final vote count, the DP secured 12 of the 16 contested mayoralties and governorships, while the PPP took four, including the capital. In Busan, DP candidate Jeon Jae-soo edged out the PPP's Park Heong-joon by a slim margin — a symbolically heavy loss for conservatives in their traditional southern base.

In Gyeonggi Province, veteran DP lawmaker Choo Mi-ae defeated the PPP's Yang Hyang-ja by a wide margin, becoming the country's first woman to head a provincial government.

By-elections deepen DP dominance

Of the 14 parliamentary by-election seats contested concurrently, the DP won nine, the PPP four, and an independent took one. Thirteen of the 14 seats had previously been held by the ruling party, so the loss of four was viewed as a minor dent to its majority in the 300-member National Assembly.

Former PPP leader Han Dong-hoon, who contested as an independent, secured an Assembly seat. In contrast, Cho Kuk, leader of the liberal Rebuilding Korea Party, narrowly lost the closely watched Pyeongtaek-B race to the PPP's Yu Eui-dong in a three-way fight that also featured the DP's Kim Yong-nam.

A sharp swing from 2022

The outcome marks a striking reversal from the 2022 local elections, when the then-ruling PPP took 12 of 17 major mayoral and gubernatorial posts a month after former President Yoon Suk Yeol assumed office. Yoon was sentenced to life imprisonment by a district court in February over his failed martial law bid of December 2024 — an episode the DP repeatedly invoked during the campaign, urging voters to deliver judgment on what it called the “remnants” of “insurrectionist forces.”

In Seoul, the DP won 17 of the city's 25 district chief posts, a sharp improvement from the eight it secured in 2022. Nationally, the DP took 119 of 227 district chief positions against the PPP's 95, with the rest going to independents and a minor party.

Ballot shortage controversy

The elections were partly marred by an unprecedented ballot shortage at 14 polling stations in parts of Seoul, prompting temporary suspensions of voting, with some voters reportedly leaving without casting their ballots. The PPP swiftly demanded that the National Election Commission halt counting and consider a revote, citing poor election management.

Voting ran from 6 am to 6 pm at 14,288 polling centres nationwide, with one affected booth in Songpa Ward extended to 10 pm. Also at stake were 16 education superintendent seats, 227 heads of local governments and roughly 4,000 local council members.

What happens next

The verdict is widely expected to embolden the Lee administration to accelerate its legislative reform push, while leaving the PPP with the harder task of rebuilding a conservative base still reeling from Yoon's ouster. Attention now shifts to how the NEC responds to the Seoul ballot complaints, and whether the opposition can convert local discontent into a coherent national counter-narrative.