While the literature on directly elected mayors has largely neglected the relationship between mayors and their parties, studies of party transformation have generally ignored how changes in local democratic rules and practices affect parties. This article addresses these questions using a qualitative case study of the relationship between mayors and the three faces of their parties (in local public office, local central office and on the ground) in Genoa and Lausanne. Based on interviews with the mayors, elected representatives and party members, it finds in the two cases that, as long as these mayors can count on high levels of popularity and are not nearing the end of their term, they are 'party detached'. When these factors do not apply and/or party institutionalization increases, the relationship with the party in local central office (although not with the party in local public office or on the ground) becomes more significant.