This chapter shows how shared public values shape the nature of political debate and public policy decisions, and discusses the importance of ideology in political debate and action. The debate over welfare was affected profoundly by public images about those who depended on welfare. Public opinion is supposed to shape the outcomes of government action in a democracy, so "what the people think" is a matter of great importance to. The chapter examines the core traits of liberal and conservative ideologies that dominate American political discourse. It assesses the dimensions of public opinion, how it is shaped, and its effects on political debate and policymaking and examines the role of mass media in deciding which issues dominate the national agenda of debate and action. A perennial debate in American politics is whether members of the mass media, particularly reporters, display any systematic political bias.