I situate this dissertation and its contributions at the edge of the literature on interest group political behavior and congressional responsiveness. In particular, I use new strategies and tools to study interest group influence. In the first essay, I find that a machine-learning text-analysis detects latent patterns in the frequency of lobbying by the telecommunications industry in 2015. Meanwhile, members of Congress primarily focus on healthcare and taxes when they discuss policy issues on social media. In the second essay, I measure the change in political behavior of interest groups by ideology after the surprise result of the 2016 presidential election. The evidence suggests there was an increase in political spending by ideologically polarized interest groups shortly after the election. Finally, the cornerstone of this dissertation evaluates the results of two field experiments measuring congressional responsiveness to issue advocacy with a non-profit, non-partisan political advocacy organization. Counter to expectations in the interest group literature, I find that members of Congress are responsive on social media to interest group requests on a low-salience, non-partisan issue. These findings have important implications for representation and responsiveness in the U.S. Congress by highlighting areas of research that need further study and deeper evaluation.

The lobbying of Parliament and the Government in the United Kingdom by wealthy or influential groups and individuals raises concerns about corruption and political equality. Professional lobbying is available mainly to those with significant resources and is often the most effective means of influencing decision-makers. Unchecked, it corrodes public trust in core public institutions. This thesis argues that the problems attending the lobbying of Parliament and Government in the UK need to be identified and understood more clearly so that targeted regulatory solutions can be determined. Currently, lawmakers, organisations and academics have struggled to propose clear pathways for identifying the main issues and understanding them. This is due to a failure to agree on the nature and scope of the central problems associated with lobbying, the relationship between them, and how they are relevant to the model of democratic government in the UK. To overcome this, an analytical framework called ‘institutional diversion’ is developed, tested and evaluated. The framework is developed from institutional corruption literature in the United States and is divided into three parts. Part 1 provides elements which help to identify specific lobbying concerns and provide a rich account of the underlying issues. Part 2 articulates a test to determine whether the identified problem in Part 1 causes a diversion from the purpose of the relevant public institution. It is argued that the critical purpose of decision-makers in Parliament and the Government is to ‘act in the public interest’ and that a diversion from that purpose can be tested using the two criteria of ‘integrity’ and ‘objectivity’. Further, it is not sufficient for a framework to simply identify and help to understand the concerns with lobbying. The logical next step is to identify solutions, and that process must also be rationally guided. Therefore, guidelines are developed from an analysis of an interview with the Registrar of Consultant Lobbyists in the UK conducted specifically for this thesis. The guidelines are intended to help future reform analyses by highlighting the practical and political restrictions within which solutions must be developed otherwise they will be unlikely to succeed.