The presidential nominee for South Korea's minor progressive party announced her exit from the race Monday and threw her support behind the liberal front-runner.

At a press conference in Seoul, Sim Sang-jung of the Progressive Justice Party said she hopes her resignation will be a boost to Moon Jae-in of the center-left main opposition Democratic United Party, who "effectively represents the liberal camp."

The 53-year-old formerly led and served as the floor leader of the Unified Progressive Party before it disintegrated due to factional infighting over rigged party primaries.

Moon, a 59-year-old former human rights lawyer who served as chief of staff to late President Roh Moo-hyun, expressed appreciation for her support and said he would meet with her soon for policy coordination.

Her exit came on the hills of independent Ahn Cheol-soo's high- profile departure from the race last week, which virtually made Moon a sole candidate to face off conservative favorite Park Geun- hye.

With the withdrawals, the upcoming election has come down to a traditional match between the ruling party seeking to hold on to the conservative rule and the center-left opposition party determined to put an end to it.

The election is slated for Dec. 19, with President Lee Myung- bak constitutionally barred from seeking re-election.