The literature on South Korean elections has shown that voters’ region, ideology, and generation shape their preferences at the polls. Few studies, however, have investigated the long-term effects of these variables or the difference in the effects of ideology and generation between regions. In this article, we generate theoretical expectations of Korean voters’ voting behavior, analyzing cleavage structures in the party system since democratization, and we then examine the interactive effects of region with ideology and generation across voters from Gyeongsang and Jeolla, in six presidential elections from 1992 to 2017. We find that ideology and generation have stronger effects among Gyeongsang voters than among Jeolla voters. To be specific, ideology and generation often divide Gyeongsang voters, especially when the Democratic Party nominates a presidential candidate from Gyeongsang; Jeolla voters are more homogeneous in their support for the party, regardless of their ideology and generation.