The media environment has changed dramatically in recent years. First altered by cable news, which upended the dominance of network news, digital media has in recent years created a media landscape littered with media outlets, from new, ambitious websites like Politico to citizen media sourced on Twitter. It is unclear how or if these changes have changed the relationship between the media and the public; indeed, despite considerable attention from scholars, the interdependencies between media elements such as professional news, blogs, social media, and the public that define the modern media have yet to be unraveled. Instead, several conflicting findings have emerged: some confirm the prevailing media to public agenda setting theory, others find a reverse agenda setting dynamic, while some uncover an interactive series of processes in which diverse elements influence the media and public agendas.

I argue that modern agenda setting processes reflect a hybridized media ecosystem, with mutual interdependencies and feedback loops driving agenda creation. I further characterize the issues that are likely to emerge in particular elements and consider the role of partisanship. To test my hypotheses, I analyze longitudinal data on issue attention across five elements of the contemporary media system: survey data, Twitter, key blogs, a record of Google searches within the United States; and top professional news sources. I track attention to 25 issues across a time horizon from January 2010 through December 2013. A lagged time series analysis further identifies issue origin points and trends as issues travel across elements. In order to further illuminate this relationship, I examine three of these issues in more detail by shining a light on the media and public discussions of these issues during periods of canonical attention.

I also show how the rise of partisan media has changed the media agenda itself, with the result that different outlets attend to issues at different rates. This dissertation is therefore able to characterize the interdependencies inherent within the system that drive the public and media agendas, challenging some of the assumptions of a generation of minimal effects theories.