The author is Sam Rosenfeld and the subtitle is Postwar Architects of Our Partisan Era. Here is the bottom line:
Today’s pundits wring their hands about polarization and yearn for the halcyon days of bipartisan comity. Yet pundits of the mid-twentieth century saw that very bipartisanship as the key problem in American politics. They argued that the lack of clarity between the parties stifled progress while blurring accountability to the voters. Polarization was their solution to this problem. They thought making parties “real” in the sense that Roosevelt had meant — unified behind distinct policy agendas that were clear to voters — would invigorate democracy and improve policymaking. Their ideas influenced the views of key political actors on both the left and right in the ensuing decades.
This book is the story of how that happened, and it is a useful corrective for those who thinks greater partisanship is something quite recent.