Barack Obama's ascension to the presidency won't end racism, but it does mean race is no longer the dominant issue in American politics. Instead, over the coming decades, class will likely constitute the major dividing line in our society—and the greatest threat to America's historic aspirations. This is a fundamental shift from the last century. Writing in the early 1900s, W.E.B. DuBois observed, "The problem of the 20th century is the problem of the color line." Developments in the ensuing years bore out this assertion. Indeed, before the 1960s, the decade of Barack Obama's birth, even the most talented people of color faced often insurmountable barriers to reaching their full potential. Today in a multiracial America, the path to success has opened up to an extent unimaginable in DuBois's time.

Obama's ascent reflects in particular the rise of the black bourgeoisie from tokens to a force at the heart of the meritocracy. Since the late 1960s, the proportion of African-American households living in poverty has shrunk from 70 percent to 46 percent, while the black middle class has grown from 27 percent to 37 percent. Perhaps more remarkable, the percentage who are considered prosperous—earning more than $107,000 a year in 2007 dollars—expanded from 3 percent to 17 percent.

Yet as racial equity has improved, class disparities between rich and poor, between the ultra-affluent and the middle class, have widened. This gap transcends race. African-Americans and Latinos may tend, on average, to be poorer than whites or Asians, but stagnant or even diminishing incomes affect all ethnic groups. (Most housecleaners are white, for instance—and the same goes for other low-wage professions.) Divisions may not be as visible as during the Gilded Age.