Moon Jae-in of the liberal Democratic Party maintained his lead as the presidential front-runner, while a longtime rival nearly doubled his approval rating to come in second, a poll showed Friday.

Moon, a former leader of the largest party in parliament, garnered 31 percent in the survey conducted from Tuesday to Thursday, posting the same figure as the previous week, according to Gallup Korea.

Rep. Ahn Cheol-soo of the centrist People's Party, however, jumped 9 percentage points to 19 percent, reflecting a trend in other recent surveys.

The former software mogul may have absorbed some of the supporters of South Chungcheong Province Gov. An Hee-jung of the Democratic Party as he appears set to win his party's nomination next week, according to analysts.

An, who for weeks ranked second, dropped to third place with 14 percent, down 3 percentage points from last week.

Other contenders in the May 9 election are Seongnam Mayor Lee Jae-myung of the Democratic Party, who ranked fourth with 8 percent, followed by South Gyeongsang Province Gov. Hong Joon-pyo of the conservative former ruling Liberty Korea Party at 4 percent and Rep. Kim Jin-tae of the same party at 3 percent.

The survey was conducted on 1,010 voters nationwide and had a margin of error of 3.1 percentage points at the 95 percent confidence level. (Yonhap)