Main opposition presidential candidate Yoon Suk-yeol is leading his ruling party rival Lee Jae-myung with 40.6 percent public support against Lee's 36.7 percent, a survey showed Monday.

Yoon of the People Power Party (PPP) gained 6.5 percentage points from the previous week, while Lee of the Democratic Party lost 3.4 points, according to the Realmeter survey conducted on 3,031 adults from Jan. 9 to 14.

Yoon led Lee by 3.9 percentage points, which was outside the margin of error of plus or minus 1.8 percentage points at a 95 percent confidence level.

In the previous survey, Lee was ahead of Yoon by a margin greater than the margin of error.

Realmeter said the reversal was likely due to a series of developments favorable to Yoon, including the resolution of a feud inside the PPP campaign committee and the abrupt death of an activist who raised corruption allegations against Lee.

Ahn Cheol-soo, the presidential candidate of the minor opposition People's Party, added 1.8 percentage points to post 12.9 percent, continuing his upward streak.

Sim Sang-jeung of the minor progressive Justice Party earned 2 percent.

In the hypothetical scenario of Yoon and Ahn merging candidacies and Yoon emerging as the unified candidate, Yoon had 45.2 percent support, followed by Lee at 37 percent and Sim at 3.8 percent.

With Ahn as the unified candidate, Ahn had 42.2 percent support, followed by Lee at 34.3 percent and Sim at 3.2 percent.

Asked to pick the candidate most likely to win, 46.2 percent chose Lee, while 41.9 percent picked Yoon and 5.7 percent Ahn.

Lee's rating was down 6.6 percentage points, while Yoon's was up 7 points. (Yonhap)

For more information regarding the survey results go to the National Election Survey Deliberation Commission homepage.