Updating cleavage theory for the twenty-first century

Contemporary cleavage research has linked 'socio-cultural' conflicts mobilised by new left and far right parties to structural divides in post-industrial knowledge societies. Contributions in this special issue seek to better understand the micro-foundations of a new cleavage as well as its strength and character compared to classic cleavages such as class and religion. Here, we outline three fundamental puzzles of twenty-first century cleavage formation. First, how does a new cleavage durably structure politics without the kinds of mobilising organisations so central to previous cleavages? Second, how do contemporary dynamics of party system fragmentation affect the process (and theorization) of cleavage formation? Finally, what should we make of the indirect mobilisation of structural divides today, where, for example, education empirically predicts political behaviour but is distant from voters' self-understandings or parties' rhetoric? These puzzles are prompting updates to cleavage theory, which in turn serve to revisit major cleavages of the past.