Moon Jae-in of the main opposition Democratic Party remained unchallenged in a presidential opinion poll despite a slight fall, data showed Friday.

In the survey conducted this week by Gallup Korea, Moon received an approval rating of 32 percent, down 1 percentage point from the previous week.

South Chungcheong Gov. An Hee-jung of the same party, stayed in second with 21 percent. His support also decreased 1 point.

The two liberal contenders have bickered over a range of issues from the planned deployment of a US missile defense system to Ahn's conciliatory gestures toward conservative politicians even including allies of President Park Geun-hye.

The third place was shared by Acting President and Prime Minister Hwang Kyo-ahn, Rep. Ahn Cheol-soo of the People's Party and Seongnam Mayor Lee Jae-myung of the Democratic Party, all of whom scored 8 percent.

Hwang and Ahn saw their support fall 1 point, while Lee's climbed 3 points.

Rep. Yoo Seong-min of the Bareun Party continued to slump at 2 percent.

Nineteen percent were undecided or refused to answer. The survey was conducted on 1,006 adults with a margin of error of plus or minus 3.1 percentage points this week. (Yonhap)