This chapter raises a number of hypotheses regarding the impact of new forms of partisan engagement on the evolution of the two largest mainstream British political parties. Based on quantitative as well as qualitative data, the chapter provides an analysis of the new relationships between traditional parties and their members, supporters as well as the wider public. This discussion will take place within a supply and demand conceptual framework to explore the specific ‘bottom-up’ strategies deployed by the Conservative and Labour parties in the face of widespread membership decline, and in their attempt to rekindle political engagement and devise new ways to strengthen their links with the public, giving the impression that they are thus moving away from the oligarchic structure of party organisation. The analysis will show however that the new, looser and more episodic forms of party membership do not replace the older forms but complement them and that the influx of new-style members and supporters comes with its own challenges. The main issue at stake is therefore whether the changes will lead to a strengthening or a weakening of the ties between citizens and political parties.