Busan's election commission holds campaign event with young students to promote voter participation at a school campus in Busan's Geumjeong District, Wednesday. Yonhap

While the by-elections scheduled for Oct. 16 are seen as a "mini-election" for only four local government heads and the education chief of Seoul, both the ruling and opposition parties are approaching it seriously, as it marks the first opportunity in six months since the general elections to gauge public sentiment.

This election will also be the first test of the new leadership of both the ruling People Power Party (PPP) and the main opposition Democratic Party of Korea (DPK). A loss in any key stronghold regions could significantly undermine their leadership. As a result, party leaders are amplifying their rhetoric, framing the elections as an "all-out battle." This heightened tension could potentially escalate into a deeply polarized, factional showdown.

The Oct. 16 by-elections will be held to select the heads of Incheon's Ganghwa County, Busan's Geumjeong District and South Jeolla Province's Yeonggwang County and Gokseong County, as well as the superintendent of education for Seoul.

Candidate registration closed late last month, and official campaigning began on Oct. 3. Early voting will take place for two days from Oct. 10 to 11, with the main election set for the 16th.

People Power Party (PPP) leader Han Dong-hoon, second from right, hold the hands of a supporter during his visit to a local market in Incheon's Ganghwa County, Sept. 27. Yonhap

In Ganghwa County, the election is expected to be a four-way race, with candidates from the PPP, the DPK and two independents having completed their registrations. This area is traditionally considered a stronghold for the conservative party, but the situation has become more complex with the entry of former Incheon Mayor and two-term lawmaker Ahn Sang-soo, who left the PPP to run as an independent.

In Yeonggwang and Gokseong, the by-elections for county governors have evolved into a contest primarily within the opposition bloc — a race between the DPK and the Rebuilding Korea Party (RKP), a new liberal party founded by former Justice Minister Cho Kuk. The competition is particularly intense in Yeonggwang, where the candidates' past criminal records, including allegations of fraud, violence and DUI, have sparked significant controversy over their qualifications.

The by-election for the head of Busan's Geumjeong District, where the PPP is anticipated to perform strongly, will largely hinge on whether opposition liberal candidates can unite. The RKP has urged the DPK to consolidate their candidates before Oct. 15 — the day before the election — but the DPK has yet to respond.

Each party faces significant pressure to secure victories in their strongholds. A loss in any region where they are expected to perform well could result in considerable backlash. This means the PPP has a higher stake in the races in Incheon and Busan, while the DPK is under pressure to outperform both the RKP and independent candidates in South Jeolla Province's Yeonggwang and Gokseong.

Democratic Party of Korea (DPK) leader Rep. Lee Jae-myung, left, shakes hands with a supporter on the campaign trail in Geumjeong District in Busan, Sept. 24. Yonhap

Rep. Lee Jae-myung, the leader of the main opposition DPK, underscored the importance of victory in the upcoming by-elections.

"When considering their significance, the upcoming by-elections are by no means a small election: they represent a golden opportunity to remind the incumbent administration, which has ignored the people's stern warnings, of the power of public sentiment," Lee wrote on Facebook, Oct. 1.

"I urge everyone connected to Busan's Geumjeong District, Incheon's Ganghwa County and South Jeolla Province's Yeonggwang and Gokseong to participate. In these by-elections, where voter turnout tends to be low, only a fierce battle can lead to victory," he added.

This was his first public message following the prosecution's request for a three-year prison sentence on charges of witness tampering the previous day.

Now that Lee is facing two upcoming verdicts — one for the public office election law violation on Nov. 15 and another for the witness tampering case on Nov. 25 — political insiders emphasize that the outcome of the by-elections is especially crucial for Lee.

"The court ultimately cannot ignore public opinion," a high-ranking political official told The Korea Times on the condition of anonymity. He explained that if negative public sentiment against the Yoon administration is confirmed, Lee and his supporters may anticipate judicial decisions in his favor to mitigate the "judicial risks" he faces.

Conversely, if the verdicts are unfavorable, Lee "cannot avoid facing significant backlash," the official added.

If either of the two trials results in a fine of 1 million won ($758) or a prison sentence, Lee will immediately lose his seat in the National Assembly, and will be barred from running for office for five years, disqualifying him from participating in the 2027 presidential election.

Democratic Party Korea (DPK) leader Rep. Lee Jae-myung, left, and People Power Party (PPP) leader Han Dong-hoon look at each other during a meeting at the National Assembly in Seoul, Sept. 1. Yonhap

PPP leader Han Dong-hoon is also facing a pivotal moment with the upcoming by-elections.

Both the DPK and the RKP contend that a loss by the ruling party in even one district could fracture Han's leadership in the conservative party.

In a radio interview on Sept. 30, RKP Rep. Shin Chang-sik stated, "Even if the PPP wins three out of four districts, it will enter a state of internal conflict."

Similarly, DPK Rep. Jung Sung-ho remarked in another media interview, "Even if the DPK loses in one of the races for Yeonggwang or Gokseong, it won't be a significant blow. However, the situation is different for the PPP. If Han loses the election, it will be an unprecedented setback for him."

Opposition lawmakers pointed to several reasons for Han's vulnerabilities. A major factor is that his faction within the party is not particularly strong, and ongoing conflicts with President Yoon have eroded the party's cohesion, raising the likelihood of internal strife over the election results within the ruling party.

The ruling political camp acknowledges that the election results could severely undermine Han's new leadership role.

However, they also pointed out that the PPP's chances of winning either of the two regions of opposition-dominated South Jeolla Province are already considered low. Thus, losses in these counties won't create a burden for Han.

Nonetheless, if the PPP were to lose in even one of its historical strongholds, such as Busan's Geumjeong or Incheon's Ganghwa, tensions between the pro-Yoon and pro-Han factions over accountability are expected to escalate further.