Main opposition presidential candidate Yoon Suk-yeol is leading his ruling party rival Lee Jae-myung by 9 percentage points and 4 percentage points, two polls respectively showed Thursday.

Yoon of the conservative People Power Party earned 40 percent support against Lee of the liberal Democratic Party's 31 percent, according to a poll conducted on 1,012 adults from Monday to Wednesday by Embrain Public, Kstat Research, Korea Research and Hankook Research.

Yoon gained 5 percentage points from last week, while Lee lost
4 percentage points.

The gap between Yoon and Lee was outside the margin of error of plus or minus 3.1 percentage points at a 95 percent confidence level.

Ahn Cheol-soo of the minor opposition People's Party garnered 8 percent support, down 1 percentage point from last week. 

Sim Sang-jeung of the minor progressive Justice Party lost 2 percentage points to post 2 percent. 

When asked to pick the candidate most likely to win, 48 percent of the respondents chose Yoon, while 32 percent opted for Lee.

The survey also found 50 percent said an opposition candidate must win the March 9 election, while 38 percent said a ruling party candidate should win the election.

In a joint poll commissioned by major broadcasters KBS, MBC and SBS, Yoon led Lee 39.2 percent to 35.2 percent.

The gap was within the margin of error of plus or minus 2.2 percentage points at a 95 percent confidence level.

Ahn earned 8.1 percent, while Sim posted 3.7 percent.

When asked to pick the candidate most likely to win, 46.3 percent of the respondents chose Yoon, while 40 percent chose Lee.

In the hypothetical scenario of Yoon absorbing Ahn's campaign, Yoon beat Lee 43.1 percent to 36.2 percent.

In the scenario of Ahn absorbing Yoon's campaign, Ahn defeated Lee 38.5 percent to 33.1 percent.

The survey was conducted by Ipsos, Korea Research and Hankook Research on 2,006 adults on Tuesday and Wednesday. (Yonhap)