Theorists of affect and radical democracy have largely overlooked the importance of intentionally cultivating affective dynamics in the process of changing institutions. We address that lack by introducing the concept of musical groove as an intercorporeal feel for improvisational co-creation. Groove in a political context involves specific practices of modulating dynamics, receptivity, and affects in relationship to specific contexts, people, and practices to powerful effect. We explore how early democratic movements during the American Revolution sought to craft institutional forms capacious (...) enough for such democratic groove despite the fact that key intellectual leaders of the time, such as the Federalists and Benjamin Rush, feared the power of intercorporeal affective flows of democratic enthusiasm and popular improvisation. We read Rush’s critique and his efforts to diminish and control these emergences by harmonizing them in the order as a “negative image” of a radical democratic alternative that would foster improvisation and build enthusiasm for catalysing change today. We discuss how improvisation can, as Pierre Bourdieu perceived, simply function to reproduce the limits of a given socio-political game, which is deeply embedded within us as a “feel for the game” or set of affective dispositions. However, we turn Bourdieu’s own critique against itself to find openings for a habitus of political groove and democratic improvisation that he considered foreclosed. We conclude by fleshing out these insights in relation to affective dynamics among political organizing practices and modest institutional changes during a period of rich local transformation in which we participated in Durham, North Carolina. (shrink)