Via an examination of the Labour party's approach to by-election campaigning in Scotland between the fall of the first Labour administration in October 1924 and the party's return to office in May 1929, this article explores the changing horizons of British radicalism in an era of mass democracy. While traditional depictions of interwar politics as a two-party contest in which political allegiances were shaped primarily by social class have increasingly been questioned, accounts of Labour politics in this period have focused chiefly on national responses to the challenges posed by the expanded franchise. In contrast, this article considers local experiences, as provincial participation and autonomy, particularly in candidate selection and electioneering, came to be viewed as an impediment to wider electoral success, and political debate coalesced around attempts to speak for a political nation that was, as the focus on Scotland reveals, indisputably British. Often portrayed as evidence of ideological divisions, such internal quarrels had crucial spatial features, and reflected a conflict between two models of political identity and participation: one oppositional in outlook, local in loyalty, and rooted in the radical tradition, the other focused upon electoral concerns and Labour's national standing.