Many theorists assume that the openness of immigration regimes and the inclusiveness of citizenship regimes trade off. Yet, there is no consistent empirical evidence supporting this widespread assumption. In this paper, I argue that different levels of immigration-related politicization in democratic elections can explain variation in the relationship between immigration and citizenship regimes across democracies and thus account for these empirical inconsistencies. More specifically, I contend that when elections do not politicize immigration-related issues, immigration and citizenship policies are not correlated because they follow distinct logics. When politicized, however, immigration and citizenship policy-making are driven by a common logic, aligning along the cosmopolitan-nativist dimension of party politics. Therefore, rising levels of politicization should lead to an increasingly positive correlation of immigration regime openness with citizenship regime inclusiveness. I test this hypothesis using quantitative analyses across 23 Western democracies from 1980 to 2018. The results support but also qualify the argument, showing that while it is robust at the highest level of aggregation, low levels of politicization during certain periods have been associated with openness-inclusiveness trade-offs in ways that explain existing empirical inconsistencies. I conclude by expanding the theoretical argument to define the conditions under which trade-offs occur. In sum, this paper bears important implications for long-standing normative and empirical debates on national boundary regime making.