In the administrative capital of Sejong, the incumbent mayor Lee Choon-hee of the Democratic Party is aiming for a third-term.
Public officials in their 30s, 40s and 50s have traditionally leaned liberal, so the central city was once considered a safe seat for the main opposition DP.
But in this election, Sejong has become a toss-up, with Choi Min-ho of the conservative People Power Party catching up in the polls.
There are rising expectations for the region's development once Sejong fully becomes South Korea's administrative capital which is being pushed by both the main parties laying the legal foundations for setting up a secondary presidential office in the city.
This was also an election pledge made both by President Yoon Suk-yeol and the DP's Lee Jae-myung as part of achieving balanced national development.
And on Thursday, parliament's judicary committee approved a bill to do it just six days before the elections.
This was the final hurdle for the bill to be put up for a vote.
And given the bipartisan consensus, the bill will likely be passed swiftly at a plenary session, which could be held as soon as Friday.
Its approval also comes on the same day President Yoon held his first Cabinet meeting in the city.
The PPP's Choi Min-ho has rallied his supporters, pointing to the synergy he could create as mayor with the Yoon administration.
The DP's Lee Choon-hee condemned President Yoon's Cabinet meeting as lacking sincerity.
With the two days of early voting on Friday and Saturday, the two parties are going all out to win Sejong, which could also affect the surrounding Chungcheong region.
There, a total of 4 out of 17 posts are up for grabs.
Lee Kyung-eun, Arirang News.