Public support for the two leading presidential contenders -- former Prosecutor General Yoon Seok-youl of the main opposition party and Gyeonggi Province Gov. Lee Jae-myung of the ruling party -- both increased in an opinion poll released Thursday with Yoon leading Lee by a small margin.

In the poll of 2,043 voters conducted by Realmeter on Monday and Tuesday, Yoon of the People Power Party (PPP) retook the lead with support from 28 percent of the respondents, closely followed by Lee of the Democratic Party (DP) with 27.6 percent.

Yoon, who had led Realmeter's presidential hopefuls poll since February, lost the lead to Lee in the previous poll conducted in the second week of September.

Yoon's and Lee's popularity rose by 3.8 percentage points and 0.6 percentage point, respectively, from the previous poll.

The gap between the two leading presidential candidates was a mere 0.4 percentage point, smaller than the poll's margin of error of plus or minus 2.2 percentage points.

The two were also within the margin of error in a hypothetical two-way race, with Yoon at 42 percent and Lee at 38.3 percent.

The Seoul-based pollster said the rise in the two leading contenders' popularity seems to be attributable to the rallying of their supporters amid a widening political storm over a controversial land development project carried out in the Daejang district in Seongnam, just south of Seoul, in 2015.

Lee, who was the city's mayor at the time, is suspected of having given business favors to private companies to help them join the project.

Yoon is accused of having personal connections with the owner of an asset management firm at the center of the scandal.

Both have denied their alleged connection to the case. 

Rep. Hong Joon-pyo, a five-term PPP lawmaker whose popularity recently shot up, came in third with 14.9 percent of support and former DP chief Lee Nak-yon in fourth with 12.3 percent.

In an inquiry about favorability of ruling bloc candidates, the Gyeonggi chief ranked first at 33.4 percent, closely followed by the former DP chief at 31 percent.

Among opposition bloc candidates, Yoon took the top spot with 31.3 percent of support and Hong second place with 27.8 percent.

The poll, commissioned by online news outlet OhmyNews, has a 95 percent confidence level. (Yonhap)