On 27 September 2011, Na Kyung-won who worked as the GNP's spokeswoman from 2006 to 2008 was nominated as the GNP candidate. Meanwhile, the opposition coalition unified the candidate. Independent candidate Park Won-soon, Democratic candidate Park Young-sun and Democratic Labor candidate Choi Gyu-yeop participated in the candidate unification primary, and Park Won-soon won the primary and became the nominee of the opposition coalition. On 26 October 2011, Park Won-soon was elected by 7.19%, winning 53.40% of the votes. On the other hand, Na Kyung-won won 46.21% of the votes and become second place. So, there is a saying that it is similar to the 2011 by-election in that Park Young-sun, Na Kyung-won, Oh Se-hoon, and Ahn Chul-soo, who were involved in the 2011 mayoral by-election, are running for the Seoul mayoral by-election in 2021.
