Scholarly attention to populism has expanded dramatically in recent years as insurgencies have multiplied across Western nations. In Europe this has primarily consisted of research on populist party voting, and in the US mainly on populist social movement mobilisation. Little dialogue exists between the two. A theoretical solution to the impasse is proposed, drawing upon the widespread use of grievance issue as the primary unit of analysis in research on collective action by advocacy organisations and protesters. A decomposition of issues pursued by parties allows direct comparisons between single- and multiple-issue collective actions across all types of collective action.