Over the past decade, clear evidence has been produced showing that effective constituency campaigning in British general elections can lead to better electoral performance. This evidence has challenged the received wisdom that only national campaigning is significant and that efforts at local level are meaningless rituals. Denver et al. have focused on the role of the national parties in strengthening local campaigns in target seats; Seyd and Whiteley, by contrast, have stressed the importance of local party membership. This article attempts to assess the relative electoral impact of national party co-ordination and constituency party membership and suggests that the impact of these two factors varies by party.