Over the long holiday weekend, South Korea’s ruling and opposition lawmakers campaigned across Gangseo in western Seoul, as the district is set to choose a new head in a by-election next week.

With the general election six months away, the Gangseo-gu by-election on Oct. 11 will offer insight into voter sentiment in Seoul -- a swing electorate holding some 40 seats that can determine which party will win control of the National Assembly.

Winning in Seoul will be essential for the ruling People Power Party, which is currently outnumbered 111 to 168 by the main opposition Democratic Party of Korea, to be able to give the Yoon Suk Yeol administration a much-needed legislative push when it enters its third year in office. For the first year of his term, the conservative president saw many of his major policies set back by the Democratic Party-majority National Assembly.

In Gangseo-gu, the polls have so far favored Democratic Party candidate Jin Gyo-hoon over People Power Party candidate Kim Tae-woo by a margin of around 10 percentage points. Jin served as the deputy chief of the National Police Agency until June last year. Kim, who was the district’s previous head, launched a bid to run for a second time after he lost the post over a suspended jail sentence. In May, he was convicted for leaking official secrets as he blew the whistle on the Moon Jae-in presidential office.

The majority of South Koreans see the Gangseo-gu by-election as a preview of the 2024 general election, according to a poll surveying 1,002 eligible voters from Sept. 25-26. Some 61 percent of voters surveyed by the poll responded that the results of the by-election in the Seoul district would affect next year’s election to fill the Assembly.

People Power Party leader Rep. Kim Gi-hyeon told reporters Tuesday the upcoming by-election and the remainder of the Assembly term were “the final chance” to prove to the South Korean people that his party was about “pursuing policies that actually come to life, and not empty promises.”

He stressed a “synergy between the municipal and central governments” over the weekend, rallying support for his party’s candidate for Gangseo-gu. “There is a greater potential for our candidate to enact policies that make meaningful changes, working closely with the government and the ruling party,” he said.

Speaking to reporters also on Tuesday, Democratic Party floor leader Rep. Hong Ihk-pyo said the by-election will serve as an opportunity to “teach the Yoon administration a lesson.” “This by-election will show the administration in power that the people are not happy with how they’re running the country,” he said.

The opposition floor leader said the South Korean public has “turned their backs on the Yoon administration.” “I’ve had the chance to speak to voters this holiday, and they’ve told me the current administration was failing to look after the livelihoods of people, bent only on cracking down on the political opposition,” he said.

The Democratic Party’s leader, Rep. Lee Jae-myung, is sticking to his demands that Yoon fire his entire Cabinet to “take accountability for the failures” of his first year of presidency. Lee, who rivaled Yoon in the presidential election last year, has been hospitalized since Sept. 17. He was admitted during his 24-day hunger strike that ended Sept. 23, against what he calls the “tyranny” of the incumbent administration.

The opposition leader, who is facing several trials over corruption allegations from his time as Gyeonggi Province governor and Seongnam mayor, escaped arrest ahead of the long weekend, after the court rejected the prosecutors’ request for a warrant.