This article explores the causes of the unexpected rise of the New Korea Democratic Party (NKDP). In the 1985 National Assembly election, a new party, NKDP emerged as the main opposition party, which led to the collapse of the party system manufactured by the authoritarian regime. We argue that the election results primarily aimed at restructuring the ‘opposition bloc’. The election results were less related with public outcry against the Chun Doo-hwan regime or as a punishment for the ruling Democratic Justice Party. However, the election provided a critical opportunity for the regime-challenging NKDP to unite with young people who were the vanguard of political resistance to the authoritarian regime. In that sense, the 1985 election gave an important momentum for the pro-democracy movement later. In addition, social and economic changes such as urbanization, the rise of young voters in the demographic structure, and the mass production of ‘highly educated voters’ were also important factors for the rise of the NKDP in the 1985 election.