Mike Cowburn is a postdoctoral researcher at the European University Viadrina. He works at the European New School of Digital Studies in the Chair of Digital Democracy. His research interests include intra-party factions, candidate selection, and political communication. The bookexplains how the process through which candidates run for Congress fundamentally changed during the twenty-first century. These changes then reverberated in polarizing the parties in Congress. Primaries are commonly said to drive polarization because of the people who vote in them, but he shows instead that the nomination process exacerbates polarization through the influence of elite party actors incentivizing candidates to adopt more ideological behavior.