With Uncivil Agreement, Lilliana Mason looks at the growing social gulf across racial, religious, and cultural lines, which have recently come to divide neatly between the two major political parties. She argues that group identifications have changed the way we think and feel about ourselves and our opponents. Even when Democrats and Republicans can agree on policy outcomes, they tend to view one other with distrust and to work for party victory over all else. Although the polarizing effects of social divisions have simplified our electoral choices and increased political engagement, they have not been a force that is, on balance, helpful for American democracy. Bringing together theory from political science and social psychology, Uncivil Agreement clearly describes this increasingly "social" type of polarization in American politics and will add much to our understanding of contemporary politics.