What is the role of think tanks in shaping public policy and public discourse in the United States?

In The Fifth Estate: Think Tanks, Public Policy, and Governance, James G. McGann illustrates how policymakers have come to value the
independent analysis and advice provided by think tanks and why these institutions have become key players in the American political system. Drawing on case studies that examine the role of think tanks in both foreign and domestic policy, McGann clarifies the relationship between think tank
research and the policies enacted during the Clinton, Bush II, and Obama administrations. He also describes the phenomenon known as "the revolving door," where think tanks provide former government officials an opportunity to share insights from public service, remain involved in policy debates, and continue to provide advice and commentary.

Based on their history and their level of involvement seen today, the influence of think tanks is unlikely to diminish in the coming years.