His research interests are U.S. social policy and comparative social policy, most particularly health and welfare policy. He has published four books (two as a co-author) and numerous articles and chapters. His most recent book, co-authored with Daniel Béland and Philip Rocco, is Obamacare Wars (University Press of Kansas, 2016). This book analyses the implementation of key aspects of the Affordable Care Act in the states, investigating what factors have shaped how state governments have responded to it.