Democrats and Republicans rely on partisan think tanks for policy proposals, along with the numbers and findings that justify them. How did think tank research reach a central place in our politics and how influential are they? E. J. Fagan finds that partisan think tanks like the Heritage Foundation helped polarize the congressional issue agenda and debate, replacing the non-partisan expertise that Congress used to rely on. Conservative think tanks are gearing up for a possible second Trump administration while Biden’s policy agenda remains reliant on the liberal side of the think tank establishment.