Most public opinion surveys showed ruling Saenuri Party candidate Park Geun-hye maintaining a slight lead over Moon Jae-in of the main opposition Democratic United Party (DUP), although the gap usually fell within the margin of error.
Both sides have interpreted those results to their advantage, with the opposition camp claiming they have narrowed the gap to the extent that an upset victory is likely.
The polling results were the last to be published before the Dec. 19 vote, as South Korean law bans their release in the last six days of the election period due to concerns they could disproportionately sway voter sentiment.
In past elections, the final surveys have been a reliable barometer of public opinion.
Park Geun-hye (L), Moon Jae-in. (Yonhap)
Park, the 60-year-old conservative contender, kicked off the day in Uijeongbu, north of Seoul, on a seven-stop trail that will also take her through other cities in the capital region, the northern Gangwon Province and the battleground North Chungcheong Province.
Moon, the 59-year-old liberal candidate, started the day by announcing a package of plans to boost jobs, a cornerstone of his campaign.
Speaking at a news conference at party headquarters, the former chief of staff to late President Roh Moo-hyun pledged to secure an additional 20 trillion won (US$18.7 billion) in next year's budget for jobs and welfare.
Many of the additional jobs would be created in sectors such as health care, social services, education and public safety, he said.
Moon's campaign trail is scheduled to start in the central city of Daejeon later in the day and take him through the battleground South Chungcheong Province before ending in liberal strongholds in North Jeolla Province and Gwangju.
Both candidates are expected to touch on national security issues following North Korea's long-range rocket launch Wednesday, with each side claiming to have a better grip on matters of national defense.