The official campaign for the April 24 by-elections kicked off Thursday, with much of the public and media attention focused on the three parliamentary seats up for grabs.
The elections are the first to be held under President Park Geun-hye, who took office on Feb. 25, and could serve as a litmus test of public support for the new government. The president's approval ratings have been on the wane amid public criticism over a series of unsuccessful nominations for senior government posts.
Initial public polls indicate that the ruling Saenuri Party has a clear lead over its rivals in the Yeongdo constituency of the southeastern port city of Busan and the Buyeo and Cheongyang constituency of South Chungcheong Province.
However, Ahn Cheol-soo, an independent former software mogul and contender in last year's presidential race, has been the front-runner in Seoul's Nowon C district.
If Ahn wins, he could trigger a power shift within the opposition away from the main opposition Democratic United Party (DUP), having already demonstrated his popularity and political influence ahead of December's presidential election, according to political analysts. Speculation persists that the independent could later establish his own political party.
Ahn is scheduled to launch his official campaign with a ceremony in front of a department store in his district later in the day.
His ruling party rival and former police chief Huh Joon-young started his campaign by helping clean streets and greeting voters on their way to work in the morning.
In Busan, front-runner Kim Moo-sung, a former Saenuri floor leader and close aide to the president, also met with voters on their way to work before holding a launching ceremony later in the day.
Also Thursday, DUP leader Moon Hee-sang and other party leaders are scheduled to visit the port city to join their candidate Kim Bi-oh for his launching ceremony.
In South Chungcheong, former South Chungcheong Governor Lee One-koo of the Saenuri Party has maintained a strong lead over his DUP rival Hwang In-seok, according to public polls.
The elections will also include contests for a total of nine seats on regional governments and councils.