Rep. Song Ho-chang quit the main opposition Democratic United Party and joined independent presidential candidate Ahn Cheol-soo’s campaign Tuesday.

The former lawyer and civic activist will co-head Ahn’s campaign office with two former lawmakers, Park Sun-sook from the DUP and Kim Sung-sik from the Saenuri Party.

The first-term legislator served as a spokesperson for Park Won-soon in last year’s Seoul mayoral by-election and has been a close communication channel between Ahn and the DUP.

“Ahn is the most adequate candidate who may achieve a power transfer and political change,” Song said in an urgent press conference on Tuesday.

This is why the people gave him as much support as the ruling Saenuri Party candidate Rep. Park Geun-hye, he claimed.

“Ahn was summoned to the political arena by the people, and yet he is left all alone to bear the political offensives against him,” Song said.

“As a person who shares his thoughts and visions, I felt deeply sorry and responsible.”

He also hinted at Ahn’s possible candidacy unification with the DUP’s Rep. Moon Jae-in.

“I offer my apologies to the party and Rep. Moon, whose sincerity I do not doubt,” he said.

“I nevertheless believe that we will eventually become one and this is indeed my biggest task.”

The snap defection of the lawmaker surprised the DUP and Moon’s election camp.

“I did not discuss the issue with anybody within the party, including Mayor Park,” Song said.

He only sent a text message to Rep. Moon, party chief Lee Hae-chan and floor leader Park Jie-won, just 10 minutes before the press conference, he claimed.

“I thank Rep. Song for his painful decision to give up his position as party lawmaker,” said Ahn.

“By achieving the transfer of power (in the presidential election), I shall prove that these good intentions can indeed win.”

By Bae Hyun-jung (tellme@heraldcorp.com)