Cynthia Farina and Gillian Metzger have posted this draft on SSRN.  Here is the abstract:

This is one of two complementary essays for a symposium honoring the work of Peter L. Strauss. Also included is the joint introduction. (The second essay is Gillian Metzger, Agencies, Polarization, and the States.) These essays engage one of Strauss’s most germinal writings, “The Place of Agencies in Government: Separation of Powers and the Fourth Branch” to consider whether contemporary polarized politics spells the end of the intricate system of multi-branch control and accountability which, Strauss argued, legitimates administrative agencies.

Political polarization has become a major focus in contemporary discussions on congressional activity and governance. The tone of these discussions has grown increasingly grim, as many political scientists, argue that a constitutional system of divided and shared powers hardens current levels of partisan warfare into legislative gridlock. Proposals for reform abound. Scholars and political commentators have called for modifications to the electoral process and to party structure, for additional oversight of the culture among members of Congress, and for increased attention to demographics and economic inequality within the electorate. These proposals sometimes conflict, and usually face daunting legal or political obstacles to adoption.

In an effort to better assess the likelihood that congressional dysfunction will be the norm going forward, this Essay reviews and synthesizes recent political science literature with the goal of sorting out what we know — and, perhaps more important, do not know — about the nature, extent, and causes of congressional polarization. The Essay begins by discussing standard metrics of congressional polarization and describing alternative approaches that challenge the standard account as overly simplistic. It then looks at historical trends to consider whether the contemporary situation is truly anomalous. Next, it considers the many theories put forth to explain the phenomenon, focusing initially on whether congressional polarization can be explained by polarization in the electorate and then moving to proposals around the electoral process, party structure and culture, and demographics. Finding little support in the literature for the notion that the challenged structures and practices are actually driving legislative polarization, the Essay concludes by suggesting that the rhetoric around congressional polarization — particularly around the likely continuation of partisan warfare and legislative gridlock — is far more negative than the existing evidence can justify.