This paper explores aspects of 'decentralized personalisation' and, more specifically, the personalisation of candidate campaigns in an open-list PR voting system. Whilst there is a body of theory on how electoral systems shape candidate orientations, the impact of electoral systems on political activism in general and the personalisation of campaign activists in particular has been largely neglected. Distinctively in a comparative perspective, the strong Finnish preferential voting system has generated intense intra-party candidate competition and this fierce co-partisan rivalry has spawned the development of personal candidate support groups (CSGs) which have become increasingly institutionalised and professionalised and represent a sine qua non for a serious candidate. All CSG activists work for a party when campaigning for a particular candidate, but is it personal allegiance or party allegiance that drives their activism? This paper is the first to investigate the phenomenon of the personal CSG and it does so on the basis of interviews with Finnish parliamentarians and CSG members. How do citizens become CSG members and are they mobilised by, or because of the candidate rather than the party?