This paper studies the effects on electoral competition of political parties relying on monetary donations and volunteer labour for their electioneering activities. It also examines whether a recorded decline in party activism increases special-interest influence on party policy platforms. Parties are shown to choose differentiated platforms in equilibrium when activists are present, despite factors drawing them together. Special-interest influence on platforms increases when a decline in activism stems from a fall in their motivation, following parties relying less upon them. This reduces procedural welfare, and potentially reduces voter welfare on policy outcomes, thus calling for more strict electoral laws.