Social democracy and social protest movements have been closely related since the rise of industrial society. This chapter discusses ideal, typical early social democratic formations and their relationships to social movements, and how these relationships changed as social democrats became reformist co-managers in democratic social market economies. Rapid cultural and social changes in occupational structures, residential suburbanisation, slow 'massification' of higher education and the coming of television obliged social democratic leaders to rely less on a 'big tent' model and more on new political technologies. The chapter also discusses more recent times social movements. Here, social democrats have had to confront the emergence of new, strong, and challenging social protest movements against a background of Europeanisation and globalisation, neo-liberal policy orthodoxies and the consequences of the huge post-2008 global financial crisis. In the new century many left-loser movements have also become parties, following the Green model.