The 20th legislative elections will be held in South Korea on 13 April, 2016 to elect members of the National Assembly. This will be the first legislative election in South Korea after a controversial Constitutional Court ruling that altered the population ratio of constituencies with the highest number of population to the lowest number of population from 3:1 to 2:1, while they also decided that the number of constituents in a certain constituency must not be more or less than 1/3 of the average number of constituents.
The number of seats that was contested in the previous election was 300, with 246 members being elected with the first-past-the-post system and 54 being elected with a proportional representation system. However, this number is expected to change before the election, as the constitutional court ruling set the deadline for the Parliamentary Committee for Constituency Delimitation to confirm the number of constituencies being contested as 31 December, 2015. A possibility of gerrymandering was suggested by the media due to the National Assembly's involvement in the boundary changes.
Another controversial Constitutional Court ruling regarding the dissolution of the UPP, based upon the Lee Seok-ki incident and its potential links to North Korea, has brought the fear of the collapse of the left-wing faction a reality. The breakdown of the UPP only left the Justice Party (South Korea) as a left-wing liberal party in the National Assembly. The KCTU, one of the most influential trade union organisations in Korea, originally strongly supported the UPP, but had to change their support towards the Justice Party. The members of the National Assembly for the Justice Party and their potential candidates are considered to have similar political views with some radical left-wing members of the NPAD, which may cause a shift in voters from the Justice Party to NPAD.