PHOTOS Mayoral by-elections: Winners and losers

Oh Se-hoon, center, the main opposition People Power Party's candidate for Seoul mayor, closes his eyes while receiving applause and affirming touches from party members at the party headquarters in Seoul, Wednesday, after exit polls showed a likely victory for him. Yonhap

Kim Chong-in, the interim leader of the main opposition People Power Party (PPP), shakes hands with Ahn Cheol-soo, who chose to drop out of the mayoral by-election race to help the PPP's candidate Oh Se-hoon, at the party office in Seoul, Wednesday. Yonhap

Park Young-sun of the ruling Democratic Party of Korea stands in the party office building in Seoul, Wednesday, after exit polls showed she would lose to her rival Oh Se-hoon in the Seoul mayoral election. Yonhap

Park Heong-joon, the Busan mayoral candidate of the main opposition People Power Party, and his wife celebrate at his campaign office in Busan, Wednesday, after a voting tally showed his likely victory. Yonhap

Kim Young-choon, right, the Busan mayoral candidate of the ruling Democratic Party of Korea, watches the votes come in at his campaign office in Busan, Wednesday. Yonhap

Acting Democratic Party of Korea Chairman Rep. Kim Tae-nyeon, center, and other party leaders watch the ballot counting at the party's office in Seoul, Wednesday. Yonhap