South Korean will be holding by-elections on April 7th municipal positions, the most notable of which will be for the Mayor of Seoul and Busan. Both Seoul and Busan saw its incumbent centre-left Democratic Party mayors suffers sexual harassment allegations. Seoul Mayor Park Won-Soon ended up committing suicide while Busan mayor Oh Keo-Don resigned. Despite a historical landslide victory in last year's legislative elections, the Democratic Party is not in good shape against a resurgent right due to scandals relating to real-estate and disputes over the reform of the prosecutors' office. Incumbent President Moon Jae-In's approval rating has fallen to 34.1%, the lowest in his administration (
http://www.koreaherald.com/view.php?ud=20210322000121).
As a result of unpopularity of the ruling party, Democratic candidates have been trailing significantly in both mayoral races. The only hope for Democrats (who nominated a female candidate, Park Young-Sun) in the Seoul mayoral race was that the right was divided between former Seoul mayor Oh Se-Hoon of the conservative People's Power Party and Ahn Cheol-Soo of the centrist People's Party. However, Oh and Ahn managed to come to an agreement to unite behind the candidate who polled the most support. Today Oh Se-Hoon was selected as the candidate of the unified conservative bloc, following a telephone poll of Seoul residents (
https://en.yna.co.kr/view/AEN20210323002751315?section=national/politics). This is bad news for Ahn, who has had a meandering and largely unsuccessful political career for the past 10 years. Conversely, should he win it will be something of a homecoming for Oh who resigned 10 years ago as mayor after losing a referendum on a free school lunch measure which he opposed. It was in that mayor by-election that Park Won-Soon was first elected and where Ahn first seriously considered a political run before declining to do so. Should the conservatives win, it will doubtlessly be seen as a sign of the right's resurgence after their catastrophic collapse following the impeachment over former President Park Geun-Hye.
Wikipedia has a fairly good article on S. Korean politics:
https://en.wikipedia.org/wiki/2021_South_Korean_by-elections