This article looks at Bernard Williams’s relevance to particular debates in constitutional theory about the legitimacy of two competing models of institutional design: political constitutionalism which endorses giving the final say on the meaning of constitutional rights to legislatures; and legal constitutionalism which endorses giving the final say on the meaning of rights to courts. Recent defences of political constitutionalism have made claims about the realism of their accounts when compared with legal constitutionalism and have co-opted Bernard Williams’s realism to (...) support their case. This article examines these claims, concluding that these accounts of political constitutionalism rely on a distinctly non-Williamsian form of political moralism in that they assume a legitimacy for political constitutionalism which is prior to politics and political disagreement. It offers an alternative defence of political constitutionalism, a partial defence, which, it argues, is closer to the realism of Bernard Williams than these accounts. (shrink)