Aidan's approach to political economy stems from the comparative politics tradition. Rather than seeking generalised laws to explain the cross-national variation in national varieties of capitalism, this research tradition seeks empirical case knowledge of the causal processes through which institutions and politics interact to produce variation in public policy outcomes. Aidan applies this theoretical framework to the study of national growth regimes within the Eurozone, wage setting, wealth and income inequality, labour markets, housing markets, industrial relations and the welfare state.

Methodologically, Aidan's research combines large N statistical analysis with small N comparative case studies. In particular, Aidan and his co-authors are interested in how policies and institutions change over time. They use distributive lag panel models with time series data, in addition to in-depth qualitative causal process tracing analysis. Aidan has done comparative case study research on Ireland and Italy, Ireland and the Netherlands, and Ireland and Hungary. More recently, Aidan has taken an interest in using survey experiments, to test competing theories on how public policy preferences are formed. Aidan is involved in a variety of international research projects, including an EU funded project with partners in Barcelona, Florence and Amsterdam that applies the use of social network analysis to the pattern of wage setting in the pharmaceutical and retail sectors in Italy, Spain, Ireland and the Netherlands.

Aidan is also working with co-authors on projects that range from assessing the impact of rising house prices on wealth inequality in Europe; the elite politics of foreign direct investment in Ireland and Hungary; the impact of the media framing on attitudes toward corporate tax avoidance; and social pacts in Europe. In 2018, Aidan received funding from the EU to develop a Jean Monnet Centre of Excellence in the New Political Economy of Europe: Re-engaging the Street. The research and teaching project address three themes within the comparative political economy of Europe: economic governance; protest and politics; and democratic legitimacy.