This chapter examines hitherto unknown sources relating to provincial popular mobilisation in support of the ‘Leveller’ agenda in 1648. One of the chief goals is to explore a little-studied phenomenon – rural support for the Leveller programme. It will do so by exploring a region, the south-west, that has been almost entirely neglected in scholarship on concerted radical political mobilisation (David Underdown, the region’s leading historian, overlooked this material, arguing that there was no discernible Leveller petitioning activity in the area). The chapter aims to work out the underlying sources of support for this agenda, and to map the connections between mobilisation in the localities and more familiar Leveller activities in London. More broadly, the chapter seeks to clarify the relationship between Leveller agitation and the broader political revolution of 1648–49. It will be demonstrated that the coalition of militant parliamentarians who supported the ‘Leveller’ agitation in the south-west was essentially coextensive with the constituency pushing for regicide and political revolution; moreover, after the regicide, this radical parliamentarian network supplied critical local infrastructure and backing for the republican and protectoral regimes of the 1650s. The chapter thus aims to explore the popular and local basis for political revolution and republicanism.