Yoon Yeo-joon, former environment minister and veteran strategist who has long been associated with the conservative bloc, is now officially part of Ahn Cheol-soo's team, aimed at promoting his vision of "new politics."
The 74-year-old strategist is known as Ahn's political mentor.
"Former environment minister Yoon Yeo-joon is firmly convinced that Korea is in need of reasonable reform."
Yoon said he felt a sense of responsibility to support Ahn.
"I've been thinking that the constant confrontation between the two rival parties has long divided the country into two. I also thought the advent of Ahn Cheol-soo was a historical inevitability."
Yoon says the ruling Saenuri Party and main opposition Democratic Party are the politics of the first and second generations.
He said the ruling party still imitates first generation politics, which had been authoritarian and nationalistic.
Yoon said the Democratic Party has not overcome the street politics of popular democracy of the second generation.
The Democratic Party fired back, saying Ahn must first show what his new politics are really about.
"Ahn Cheol-soo has not revealed whether the color of his so-called new politics is red, blue or yellow. Merely criticizing the two rival parties will not answer all the questions people have for him."
The Saenuri Party took aim at Yoon Yeo-joon, calling him an outdated figure who has migrated from one political camp to another.
"We have deep doubts about whether Yoon Yeo-joon is the right person for Ahn Cheol-soo's new politics."
During the 2004 general election, Yoon helped President Park Geun-hye then-chairwoman of the Grand National Party, now the Saenuri Party, restore the party's approval ratings which had tumbled after it attempted to impeach late president Roh Moo-hyun.
Kim Yeon-ji, Arirang News.