South Chungcheong Gov. An Hee-jung, also of the Democratic Party, took second place with 15.6 percent, up 1.5 percentage points from the previous week.

He was trailed by Ahn Cheol-soo of the centrist People's Party with 12 percent and Seongnam Mayor Lee Jae-myung of the Democratic Party with 10.8 percent.

The election landscape has tilted strongly in favor of the liberal camp after conservative President Park Geun-hye was removed from office over a corruption scandal earlier this month.

Moon, who lost to Park in the 2012 election, has emerged as the favorite contender across regions and generations.

He posted top ratings not only in the southwestern Jeolla region, the liberal stronghold, but also in the southeastern Gyeongsang provinces and the capital area including Seoul.

Voters aged 60 and above also chose Moon over South Gyeongsang Gov. Hong Joon-pyo of Park's Liberty Korea Party. The conservative party is largely supported by older generations with an aversion to North Korea.

The conservatives had pinned their hopes on Acting President and Prime Minister Hwang Kyo-ahn, who garnered double digit approval ratings in the weeks leading to Park's ouster. Hwang, however, announced last week that he would not run for president.

Hong absorbed the largest share of Hwang's popularity, climbing 6.2 percentage points to post 9.8 percent.

The most favored party was the Democratic Party with 50 percent, the first time it has attained that figure. The People's Party followed with 12 percent and the progressive Justice Party with 6 percent, each beating their conservative counterparts Liberty Korea Party (11.6 percent) and its spinoff Bareun Party (4.8 percent), the poll showed.

The survey was conducted from Wednesday to Friday on 2,025 adults nationwide and had a margin of error of 2.2 percentage points at the 95 percent confidence level. (Yonhap)