Constitutions are a key element of the normative script of the modern state. All constitutions lock in rights. Most include social provisions. Some are more generous than others in this regard. But none come close to the Portuguese Constitution of 1976 in the length and detail of its list of social and economic rights. Prevailing theories of institutional origins have generated hypotheses to account for the constitutionalization of second-generation rights. But they fall short of providing a full understanding of constitutionalization and the accompanying emergence of judicial review. Outlier cases, such as the Portuguese, are even more poorly explained by extant explanations. In this article, we test them against the Portuguese case, which, whenever appropriate, is compared with Spain. In doing this, we aim at two things: first, to identify shortcomings in the most familiar frameworks, theories, and hypotheses concerning the causal mechanisms leading to the inclusion of social and economic rights in constitutions; second, to propose alternative explanations where existing ones prove inadequate or insufficient.