Ahn Cheol-soo, a powerful potential candidate for Seoul mayor, announced Tuesday that he has decided against a run and will instead back a leading liberal activist in the upcoming election. The announcement came right after Ahn met with the lawyer-turned-activist Park Won-soon over which of the two should run as a unified candidate in October\'s by-election. Ex-mayor Oh Se-hoon quit last month after failing to block an opposition-led free school lunch program in the city\'s first-ever referendum. \"Park has devoted to himself to our society, blooming new flowers in grassroots activism. I believe he can perform better than anyone else as Seoul mayor,\" Ahn said at a joint conference with Park. \"I have decided not to run for Seoul mayor.\" Ahn, 49, a doctor-turned-computer expert who founded South Korea\'s best-known anti-virus software firm Ahnlab, is widely popular, especially among young Koreans, due in part to his clean image. Surveys have put him well ahead of other possible contenders from both the ruling and opposition parties. \"I considered the high expectations put on me as people expressed their enthusiasm for a change in leadership through (their support),\" said Ahn, who currently serves as dean of the Graduate School of Convergence Science and Technology at Seoul National University. \"I will not forget their expectations and hope to repay them by living an honest and sincere life.\" Park, a self-claimed \"social designer,\" founded the People\'s Solidarity for Participatory Democracy, one of the country\'s largest civic organizations, in 1994 with the stated goal of reforming politics through grassroots activism. Park thanked Ahn for his support. \"We spoke our true feelings and made a beautiful agreement, the likes of which cannot be seen in the political circle,\" Park said. The two have been close since 2003 when Ahn participated in a Park-led donation campaign and later served on the board of directors for the Beautiful Store, a chain of charity thrift stores founded by Park. Now, all eyes are on whether Park will run as an independent candidate or compete for the liberal camp\'s candidacy. Although Park has not yet announced his bid to join any political party, he is widely considered a liberal candidate with access to a broad network of civic activists and non-governmental organizations. Han Myeong-sook, the nation\'s first female prime minister, currently leads opinion polls within the DP, while several others lawmakers are being considered potential candidates. Political analysts expect that Ahn\'s backing would raise Park\'s low approval ratings. In the latest surveys, Ahn received nearly 40 percent support among Seoul residents, while Park registered a rating of less than 5 percent. \"Until not long ago, voters even didn\'t know that Park existed. He is better known now compared to a few days ago,\" said Lee Taek-soo, director of the research firm Realmeter. \"About 60-70 percent of Ahn\'s supporters will back Park.\" Other political watchers expressed doubts over the \"Ahn effect\" on Park, saying voters have different expectations for the entrepreneur and the liberal activist. The October by-election has drawn close attention as it is widely seen as a litmus test of public sentiment ahead of parliamentary elections planned for next April and the presidential race set for December 2012.