In a condition of genuine egalitarian inclusion, a “constitutional conception” of popular sovereignty derived primarily from the “constitutional patriotism” associated with Jürgen Habermas can resolve the key challenges associated with the countermajoritarian problem in constitutional theory as well as the problem of constituent power in democratic theory. It does so by providing a conceptual basis for an understanding of the the constitutional demos as a corporate body extending across time capable of ongoing legitimation. However, the constitutional conception cannot justify states, such as the United States, characterized by the durable exclusion of some legitimate members of the polis from political institutions. Even under the constitutional conception, the United States is not a legitimate constitutional democracy in virtue of its treatment of Black Americans. Nonetheless, there is an important tradition in Black American constitutional thought, beginning with Frederick Douglass, which represents American constitutional institutions as conditionally worthy of attachment in virtue of their latent normative potential. The correct conception of constitutional legitimacy for the United States combines Douglass's insights, and those of his intellectual heirs, with those working in the tradition which Habermas represents.