The 2016 US election saw Twitter emerge as a serious and significant political communication variable for candidates. This book provides a social network analysis and a content analysis of midterm Twitter communications. It investigates whether political campaigns in a sample of toss-up Senate races emerged as authorities on a platform, who were the opinion leaders on Twitter discussing the midterms, and what content emerged in that discourse. Using a multi-method approach incorporating timely data, this book ultimately raises new questions about the intersections of political communication and social media platforms.