PLATO developed new theory of what it would be for the European Union to experience. As set out in its living review, PLATO conceptualised legitimacy crisis as a condition where a political order is unable to satisfy all necessary conditions for its legitimacy simultaneously. PLATO then used that definition to develop three models of what it would be for the EU to experience a legitimacy crisis: where the EU cannot simultaneously satisfy all necessary conditions to be directly and democratically legitimate with citizens (model 1); where it cannot simultaneously satisfy all conditions necessary for it to be indirectly legitimated by its member state democracies (model 2); and where it cannot simultaneously satisfy all conditions necessary for input, throughput and output legitimacy (model 3).
To use those three models to build new theory of what it would be for the EU to experience a legitimacy crisis, PLATO made two methodological innovations. First, it developed methods of investigating legitimacy crisis through case studies structured along three dimensions: the one corresponding to core standards and conditions needed for democratic legitimacy, namely public control with political equality, participation, representation, accountability, a public sphere, civil society relations, and a defined democratic political community; another dimension consisting of behaviours and attitudes that can be used to investigate the legitimacy of any political system: support, trust, awareness of the political system, compliance, complaint, protest; a final dimension consisting of actors with whom the EU needs to be legitimate: member governments, parliaments, citizens, officials, courts and civil society actors. Each of the 15 PhDs investigated a different combination of standards, behaviours and actors along those dimensions. Second, PLATO adapted a range of social science methods – process-tracing, focus groups, content analysis, and some quantitative methods - to the investigation of theoretical expectations of legitimacy crisis.
Using that research design and those research methods, the 15 cases find little support for the idea that the Union has experienced a legitimacy crisis. In contrast there is some evidence of adaptation to changing conditions of legitimation or of relegitimation.