These numbers remind us of the extent to which the continued Jewish commitment to the Democratic Party has become an anomaly. All the other ethno-religious groups that, like the Jews, formed part of the coalition forged by Franklin Delano Roosevelt in the 1930s have followed the rule that increasing prosperity generally leads to an increasing identification with the Republican Party. But not the Jews. As the late Jewish scholar Milton Himmelfarb said in the 1950s: "Jews earn like Episcopalians"—then the most prosperous minority group in America—"and vote like Puerto Ricans," who were then the poorest. Jews also remain far more...