Up for grabs are 4,016 local administrative, legislative and educational posts, including 17 metropolitan mayors and provincial governors. The by-elections also will be held to fill 12 vacant parliamentary seats.
The local elections will be held Wednesday from 6:00 a.m. to 6:00 p.m. at 14,134 polling centers nationwide, according to the National Election Commission.
Turnout for the latest two-day early voting came in at 20.14 percent, which meant more than 8.64 million out of 42.9 million eligible voters have cast ballots, according to the election watchdog.
A higher-than-expected turnout for the advance voting is drawing attention on whether turnout for Wednesday's elections could surpass 60 percent.
Turnout for local elections always has been around 50 percent, except for the country's first local elections in 1995, when it was 68.4 percent.
Rival parties ramped up their campaigns Tuesday to win the hearts of undecided voters.
The ruling Democratic Party spent the final day of the campaign period appealing for overwhelming support in five major cities that range from the southeastern port city of Busan to Seoul.
The main opposition Liberty Korea Party's Tuesday campaigns was focused on Seoul and its adjacent areas.
Pre-election polls showed that the DP is widely expected to win on the back of strong public support for President Moon and his drive for peace with North Korea.
A historic summit between US President Donald Trump and North Korean leader Kim Jong-un set for Tuesday in Singapore is viewed as a boon for the liberal DP.
Rival parties have gauged impacts of the US-North Korea summit as the local elections could be overshadowed by the unprecedented summit.
The LKP is hoping that "shy" conservative voters will come out after keeping a low profile on political issues.
The opposition party is still reeling from low public support following last year's ousting of former President Park Geun-hye due to a corruption scandal.
The biggest battleground is Seoul, in which 20 percent of the country's population of 52 million live.
Current Mayor Park Won-soon is leading the race, competing against Kim Moon-soo of the conservative LKP and Ahn Cheol-soo of the minor opposition Bareunmirae Party, according to recent polls. Park is seeking his third term.
Kim and Ahn have failed to merge their candidacies ahead of the elections as they were demanding the other party drop its bid.
Park earlier dismissed the impact of a possible merger between Kim and Ahn, expressing confidence about the elections.
"If Seoul citizens elect me, I plan to make efforts to realize a road map on exchanges and cooperation between Seoul and Pyongyang," Park told a press conference. "I will seek to visit Pyongyang as soon as possible through cooperation with the government."
As for the governorship in Gyeonggi Province, the rival parties bickered over an allegation of an extramarital affair involving a ruling party gubernatorial candidate and an actress.
Lee Jae-myung of the ruling DP is under fire following his rival's revelation that Lee allegedly committed adultery with actress Kim Bu-seon some years ago while pretending not be married.
He is leading the race for the governorship in Gyeonggi Province, an area adjacent to the capital where about 24 percent of the country's population of 52 million resides.
Lee has denied the allegations, but the scandal has shown no signs of abating as the actress continues to accuse him of lying.
The LKP is hoping that Nam Kyung-pil of its party may stage a comeback as the scandal is apparently eroding Lee's support. (Yonhap)