PPP candidate Yoon Il-hyun, center, celebrates after clinching a resounding victory in Geumjeong, Busan, the biggest battleground of this week's by-elections, Wednesday. Yonhap

The ruling and main opposition parties won crucial regional by-elections in their respective strongholds, voting results showed Thursday, sparing their leadership what could have been a stinging setback from the showdown seen as a gauge of public sentiment as President Yoon Suk Yeol is halfway through his five-year term.

Up for grabs in Wednesday's by-elections were five local administrative seats — the superintendent of the Seoul Metropolitan Office of Education, as well as the heads of Busan's Geumjeong District, Incheon's Ganghwa County, and Yeonggwang and Gokseong counties in South Jeolla Province.

The governing People Power Party (PPP) swept in its traditional home constituencies — Busan's Geumjeong District and Incheon's Ganghwa County — at a time when it seeks to recover from waning approval ratings for both Yoon and the party following its crushing defeat in the April 10 parliamentary elections.

PPP candidate Yoon Il-hyun clinched a resounding victory in Geumjeong, the biggest battleground of this week's by-elections, defeating Kim Kyung-ji of the main opposition Democratic Party of Korea (DPK).

Yoon and Kim were initially seen in a tight race after the DPK and the minor Rebuilding Korea Party successfully unified their candidacies at the last minute, but Yoon won the race by a large margin.

A loss in a home turf district could have taken a toll on the PPP and its leader Han Dong-hoon, who was elected the party's new chief in July just three months after he resigned from the position to take responsibility for the April defeat.

In Incheon's Ganghwa County, Park Yong-cheol of the PPP won against DPK's Han Yeon-hee.

Cho Sang-rae of the DPK won the race for Gokseong County chief.

In a three-way battle with two minor parties, DPK's Chang Sae-il took the win in Yeonggwang County.

Meanwhile, Jung Keun-sik, a progressive and professor emeritus of sociology at Seoul National University, was elected the education chief of Seoul, leading the race against Cho Jun-hyuk, a conservative and former one-term lawmaker.

The by-election for Seoul's education chief took place after left-leaning predecessor Cho Hee-yeon received a suspended prison sentence in August for abuse of power and was stripped of his post. Cho had served in the top education office post since 2014.

In a Facebook post, PPP leader Han portrayed the election outcome as an opportunity for his party and the government to undergo "change" and "reform."

"We will not miss out on this precious opportunity bestowed to us in this difficult situation," Han wrote. "In tune with people's wishes, (I) will spearhead efforts needed to bring about change and reform in the government and the ruling party. I, myself, and the party will first undergo change and reform."

Former President Lee Myung-bak casts his ballot at a polling station in Seoul on Oct. 16, as the by-election to elect a new superintendent of the Seoul Metropolitan Office of Education begins. Yonhap

Also on Facebook, DPK leader Lee wrote that his party will do its utmost for the sake of people's everyday lives.

"Democracy can bloom on a solid footing when a local self-governing system plays its role," Lee said. "Taking the will of people expressed through the by-elections, I will take a more leading role to forestall any government retrogression and protect citizens' lives."

Voter turnout in Wednesday's by-elections was tentatively tallied at 24.62 percent.

Out of a total of 8.6 million eligible voters, 2.1 million cast their ballots at 2,404 polling centers nationwide, the National Election Commission (NEC) said after voting stations closed at 8 p.m.

The final tally included the result for the two-day early voting last week, at 8.98 percent.

By region, voter turnout in the by-election for Seoul's education chief came to 23.48 percent.

The turnout for the four other local administrative seats was estimated at 53.9 percent, which is higher than the 48.7 percent logged in Seoul's Gangseo Ward chief by-election last year and 50.9 percent in the 2022 local elections.

Observers say the election could test the leadership of PPP and DPK chiefs, Han and Lee Jae-myung, respectively, who are considered the next presidential candidates.

The outcome of the election could also shape the second half of President Yoon's five-year term, as the opposition intensifies its political offensive against the PPP and the president, with some even raising the possibility of Yoon's impeachment. (Yonhap)