This article asks whether we can identify a vitalistic undertow in Friedrich Nietzsche’s philosophy that would make sense for contemporary political and constitutional theory as well. The arguments are presented by contrasting Nietzsche’s philosophy with the social theory of Herbert Spencer. After an introduction, the first main part discusses Spencer and his so-called ‘organic analogy’ in which he draws parallels between natural organisms and the body politic. Spencer’s social theory is a paradigmatic example of vitalism and organic state theory and, (...) as a counterpoint, can help tease out Nietzsche’s vitalism as well. The article then examines Nietzsche’s admittedly fragmentary encounters with Spencer and his flirtations with vitalism and organic state theory. In the conclusions, the reconstructed narrative about Nietzsche’s vitalism is linked with Nietzsche’s main philosophical works in the hope of provisionally extracting a Nietzschean ‘constitutional theory’ from his notion of will to power. (shrink)