The persistence of the regional party system is puzzling in South Korea with its strong nation-state, homogeneous society, and three decades of democratic practice. To explain this interesting puzzle, this study claims that Korean regionalism has more dimensions than identified in prior studies and this social basis accounts for the persistence of the regional party system. We apply the multidimensional model of regionalism to the 2014 local elections and find that specific components of regionalism vary systematically across regions. More importantly, our analysis shows that regionalism is the most important determinant of partisanship among Korean voters but it has different dynamics across regions and generations. Our in-depth study sheds fresh light on the updated nature of Korean regional politics and makes a significant implication about nationalization of Korean politics.