Frances Lee examines a puzzle in American politics: why has Congress become increasingly partisan since the 1980s, even on issues without clear ideological stakes? Her answer is close competition. Since 1980, control of Congress has been genuinely uncertain, with both parties having realistic hopes of winning majorities. Lee argues that this competitive environment, rather than ideological polarization, drives congressional behavior. When majority control seems within reach, both parties prioritize political optics over bipartisan cooperation, turning every vote into a campaign opportunity. She demonstrates this through careful analysis of congressional voting patterns, showing that partisan conflict increases on issues where there's no obvious liberal or conservative position. Lee, a political scientist at Princeton, draws on interviews with members of Congress and detailed legislative history to show how the pursuit of majority status shapes institutional behavior. The book challenges accounts that blame polarization on ideological sorting or gerrymandering, pointing instead to the strategic incentives created by electoral competition itself. This is essential reading for anyone seeking to understand why Congress seems unable to function, and why appeals to bipartisan comity miss the structural dynamics that make it unlikely.