In his very thoughtful review, Elliot Posner provides a strong summary of The Politics of Fiscal Federalism while also highlighting some gaps in the argument and areas for further research.

First, Posner correctly notes that “systems of governance with multiple levels frequently arm social democrats in at least some subunit jurisdictions with additional resources that enable them to fend off pressures from policy competition.” This challenges my assertion that the social democratic approach to multilevel governance generally advocates for a greater centralization of policy capabilities to offset the constraints imposed by policy competition. In the United States, a key example here is the “California Effect” in which large progressive states have been able to push beyond policy competition by using their market power to drive national standards in areas such as auto emissions.

This phenomenon was mentioned, but clearly underdeveloped, in my sections on US federalism. I cited reports that the Obama administration was becoming increasingly open to a new “progressive federalism” that sought to use the market power of blue states more strategically as “laboratories of federalism.” This has occurred in a number of areas related to both climate policy and consumer protection, and Posner is right to suggest that activists have recognized this seemingly more decentralized approach as a source of power and opportunity.

Therefore, an interesting area for future research would be whether the decentralization inherent to a “laboratories of federalism” approach is about making the best of existing decentralization or whether it represents a broader shift in the social democratic approach. For example, at the structural level, have socially democratic politicians and activists grown more in favor of subnational (over national) social programs and the use of block grants?

Another gap identified in Posner’s review is how the rise of international soft law might affect the overall argument in terms of my framework’s emphasis on left–right political competition. Important here is the clear role played by a plurality of actors in the creation of international soft law, including networks of subnational regulatory authorities. I agree with this assessment and reviewing Posner and Newman’s Voluntary Disruptions has definitely reinforced this point for me.

Although I focus on ideological competition to highlight its significance to multilevel governance, my framework does explicitly recognize that other actors and axes of political competition are relevant and, at times, more significant to explaining outcomes. Therefore, another area for further research might be in the overlap of our two books and in some of the questions I posed for Posner and Newman: To what extent does ideology determine the views of different regulatory factions toward international soft law? Does international soft law have a progressive bias because it is international or a conservative bias because it is soft? Does ideology play a role in which actors are included or excluded from the creation of international soft law?