The conventional wisdom in the literature about party democratic reforms is that the party dealignment that characterises Western European politics since the 1980s is the main cause. Yet, this paper argues that a linear factor such as the membership decline can hardly explain alone such irregular phenomena over time. More broadly, we argue that party reforms can only be fully understood by adopting a configurational approach integrating the causal factors commonly identified in the literature as key in their explanation but which, until now, remain studied individually from each other. Hence, we conducted a fuzzy-set Qualitative Comparative Analysis (fs/QCA) of two type of democratic reforms implemented by the six Belgian mainstream parties between 1987 and 2002 modifying the leadership (characteristics) and candidate selection processes. Our results show that the decline in membership is by no means sufficient nor necessary to explain these reforms, but that they can be explained by four different combinations of conditions. ; info:eu-repo/semantics/nonPublished