Barack Obama would have lost the 2008 and 2012 presidential elections had a new set of voters not joined the American electorate—voters who brought with them a range of values that differed sharply from those of more traditional voters. These changing values—on such issues as personal social responsibility, the role of government, sexual mores, gender roles, and America’s place in the world—underpin the decisions these voters made on Election Day and provide a basis for understanding Obama’s victory. They also signify profound changes to American politics and pose elemental challenges to both the Republican and Democratic parties in coming years.