Stephen Gottlieb has posted this draft on SSRN (Georgia State University Law Review. Here is the abstract:

Changes in American law have played a major role in creating the partisan environment that many denounce. These changes have involved parallel trends in the law of political campaigns and elections and the law of mass communications. The collective impact of these changes has not been appreciated. This article brings these developments together and identifies their collective impact.
The article demonstrates how legal regulation shaped the centrism of the mid-twentieth century and regulatory shifts in media and election law shaped the partisanship of recent decades. Sensible proposals will not and should not bring the naive centrism of earlier decades back. But they might curb the excesses of contemporary politics.