This article builds on the theoretical debate over age, period, and cohort effects (APC) and explores how these factors might affect Taiwan's partisan stability. We conducted a two-level multinomial logit random effects model using survey data from 1991 to 2020 to disentangle the APC effects. Our findings challenge Converse's core assumption that partisanship strengthens with age. As a new democracy, Taiwan's party affiliations remain fluid, and we do find evidence of period effects, particularly associated with cross-Strait crises that favor the DPP. However, generational replacement is the most significant factor driving party identity changes in Taiwan. With generational replacement, the Kuomintang is burdened by the image of a century-old party. The Democratic Progressive Party (DPP) had previously fared better among young cohorts but has recently lost its support from millennials. The youngest generation increasingly refuses to associate with the traditional political parties. It seems reasonable to expect that the new generational forces will restructure the Blue–Green cleavage and expand the ideological diversity of Taiwan's party system.