The land of Saints and Shinners: under what conditions does a radical left party restrain the policy moderation of a mainstream left-wing competitor?

Sinn Féin is regularly categorized as a radical left party due to its populist rhetoric, militant past, strict internal party discipline, and the threat it poses to the constitutional status-quo in two countries. But since becoming a mainstream party, North and South, it has embraced a more moderate policy agenda. This could make it electorally vulnerable to a left challenger party through the processes of ‘pasokification’ and issue competition. The radical left Trotskyist group People Before Profit – Solidarity (PBP-S) challenges Sinn Féin in its working-class support bases and regularly criticises its moves to the centre on policy. So, to what extent does PBP-S restrain the ability of Sinn Féin to move to the centre on key economic and social issues? And under what conditions does a radical left party restrain the policy moderation of a mainstream (but populist) left-wing competitor? This article draws upon datasets from the Irish Policy Agendas Project and the Public Policy Agendas on a Shared Island project which have coded party manifestos (North and South) based on the Comparative Agendas Project coding scheme. This data will be used to compare Sinn Féin’s policy agenda (North and South) to other left-wing parties in Ireland and Europe. This analysis will support a case study of electoral competition between Sinn Féin and PBP-S in two key constituencies: West Belfast and Dublin South-West. The article theorises that being outflanked on the left is harder when the internal supply-side dynamics of a left-wing party prioritise the preservation of a working-class activist base and populist ‘authenticity’.