The end of the Civil War was a perilous moment for whiteness. Roediger writes that, in America, “scientific racism”—the sort of grand theorizing that Painter chronicles—emerged “in the context of the pro-slavery argument and as a response to abolitionism.” Whiteness survived emancipation by becoming more muscular and more self-referential: where once whiteness offered a specific legal benefit—it meant that you were unenslavable, a non-“sarvant”—now whiteness had to be its own reward. Roediger writes that some poor white laborers in the South started wearing brimless wool hats, to distinguish themselves from ex-slaves, who customarily wore straw hats. (According to one contested etymology, the sunburn such laborers suffered gave rise to the term “redneck,” which conflates race and class.)
And here's another, more contemporary bit of analysis:
A tension between élitism and anti-élitism is central to white identity, and always has been. The old race theorists couldn’t decide whether the spirit of whiteness was best reflected in the noble refinement of royalty or in the rude vitality of laborers and soldiers. Often, white identity has reflected both traditions at once, as with Emerson’s beloved Scandinavian kings, who conducted themselves like drunken brigands. The “white people” in Lander’s book [Stuff White People Like] are rich snobs who view themselves as rebels, resisting the culture of corporate greed in vague solidarity with the world’s poor. The “whitopians” in Benjamin’s book consider themselves “folksy” salt-of-the-earth types, no matter how much money they have accumulated. And “The Blind Side” is a perfect distillation of white identity as anti-élitist élitism: Leigh Anne’s husband owns nearly a hundred fast-food franchises; he’s white-collar, in a blue-collar kind of way.