As in the 1850s, social issues are the prime causes of polarization. Back then it was slavery that divided the states. Now it is the role of religion in public life, as expressed in conflicts over abortion, school vouchers, and prayer in public schools. The Republican Party once led the fight against slavery. Now it leads a different kind of moral crusade, to convert the United States into something of a Christian republic.
Nothing so divides a society as efforts to prescribe moral or religious norms.
Here s the dilemma. The religious right is a minority in the United States, with scant prospect of becoming a majority in an increasingly multicultural nation. That is splitting the country not only politically but geographically. Multicultural California, once seen as part of an emerging conservative sunbelt, has reacted by becoming a Democratic bastion. So has New England, the northern Midwest, and the prairie populist states, once the safest bastions of Republicanism.