This book argues that the congressional agenda includes many issues about which liberals and conservatives generally agree. Even over these matters, though, senators from the Democratic Party and Republican Party tend to fight with each other. What explains this discord? This book contends that many partisan battles are rooted in competition for power rather than disagreement over the rightful role of government. This is the first book to systematically distinguish Senate disputes centering on ideological questions from the large proportion of them that do not, and it foregrounds the role of power struggle in partisan conflict. Presidential leadership, for example, inherently polarizes legislators who can influence public opinion of the president and his party by how they handle his agenda. Senators also exploit good government measures and floor debate to embarrass opponents and burnish their own party's image — even when the issues involved are broadly supported or low-stakes. Moreover, the book suggests that the congressional agenda itself amplifies conflict by increasingly focusing on issues that reliably differentiate the parties. With the new president pledging to stem the tide of partisan polarization, this book provides a timely taxonomy of exactly what stands in his way.