‘Contagion theory’ suggests that the dynamics of diffusion and competition influence a party’s propensity to put forward more women candidates –or to adopt candidate gender quotas, in its more recent applications. Specifically, the equality strategies on women’s representation adopted by small (generally leftist) parties on the political periphery will incentivize other rival parties to follow suit, especially in countries with PR electoral systems. Yet while the concept of ‘contagion’ is widely used, its frequent descriptive and uncritical application to single-case studies has obscured the fact that the original conditions of the theory are often not met. We seek to re-evaluate the central propositions of contagion theory, drawing on a comparative study of West European countries. Our findings challenge and/or qualify its key tenets as currently conceptualized –including electoral system variables, the importance of small catalyst parties, and party competitiveness– and highlight the need to consider both external and intra-party factors.
