In the process of Taiwan’s democratization, scholars assert that ethnic identity, national identity, and party identity are closely linked with each other. In this paper, in addition to carefully examining the relationships among the three identities from the historical, political and sociological perspectives, we provide our hypotheses after investigating the political competition among political parties. We assert that to maximize their political benefit, political actors manipulate the definition and the content of the ethnic identity. Therefore, the ethnic identity has different meanings in different eras. Based on this assertion, we hypothesize that the relationship between the national identity and the ethnic identity is not primordially bound together, but is linked via the political competitions among parties and their engaging in negative campaigning. In order to provide empirical support for out theoretical hypotheses, we incorporate structural equation modeling with survey data. The analytical result shows that controlling for the influence of party identity, there is no significant causality between national identity and ethnic identity. In addition, after controlling for the continuity of the three identities, the pan-blue identity only causally connects with ethnic identity and the pan-green identity only connects with national identity.