A deeply researched account of how battles over civil rights in the 1960s shaped today’s partisan culture wars. In the late twentieth century, gay rights, immigration, gun control, and abortion debates all burst onto the political scene, scrambling the parties and polarizing the electorate. Neil A. O’Brian traces the origins of today’s political divide on these issues to the 1960s when Democrats and Republicans split over civil rights. It was this partisan polarization over race, he argues, that subsequently shaped partisan fault lines on other culture war issues that persist to this day. Using public opinion data dating to the 1930s, O’Brian shows that attitudes about civil rights were already linked with a range of other culture war beliefs decades before the parties split on these issues—and much earlier than previous scholarship realized. Challenging a common understanding of partisan polarization as an elite-led phenomenon, The Roots of Polarization argues politicians and interest groups, jockeying for power in the changing party system, seized on these preexisting connections in the mass public to build the parties’ contemporary coalitions.