The presidential couples, Laura and George W. Bush and Michelle and Barack Obama, standing in front of the White House, looked buff and comely in their ease and smiles. The president and the president-elect in their dark suits and blue ties and Laura and Michelle in different shades of red suggested cordiality with dignity. (If one couple looked more tanned than the other, only a churl would have imagined that an insult.)

The picture will enter the history books testifying to a new image of race in America. The victory of a black man as president changes perceptions of political possibilities. Cultural images may not follow quickly. America basks in the euphoria of an election promising a "post-racial era" and maybe new possibility for black children. It should do that, and we all hope it does, but it won't change the reality of their lives overnight. A nation's culture is not only more complex than its politics, its timetables are more difficult to manipulate. Voters point the direction they want the country to go. Cultural habits follow more slowly.

"We've had an African American first family for many years in different forms," Karl Rove observed on election night. "When 'The Cosby Show' was on (the television schedule), that was America's family. It wasn't a black family. It was America's family." Nice sentiment, but no cigar.

"The Cosby Show" was watched by blacks and whites for different reasons. The fictional Huxtables showed whites a black-middle class family that looked like "people like us." The show was an updated "Father Knows Best," reflecting white mores of the times, with a dad who was a doctor and a mom who was a lawyer.

Middle-class blacks could identify with the Huxtables, too. But this was in the 1980s, when many other blacks, not so fortunate as the family on the screen, blamed everything bad in their lives on racism, including the poverty of single mothers and high-school dropout rates. Black leaders of that day rarely touched on issues of personal responsibility. Angry critics in the black community saw "The Cosby Show" as a fairy tale to assuage white guilt rather than a tale encouraging black aspirations to the American dream.

Barack and Michelle Obama are real-life models of black achievement, but they may remind poor blacks of how different their lives are from the lives of the well-off. The president-elect's staff is talking about which expensive private school (the favorites with tuition as high as $30,000 a year) their daughters will attend. Washington public schools, among the worst in the country, are probably out.

Obama says he supports charter schools, but not vouchers, and there are several particularly good charter schools in the nation's capital. It would be a stunning act of support for them if the president-elect sends Sasha and Malia to one of them, but that's not going to happen. Like the Clintons, he will take advantage of his power and economic privilege for his children -- and who can blame him? But such a choice would only widen the perceived gap between the Obamas and the have-not blacks.

Cosby moved from depicting middle-class blacks on television to preaching to blacks about how to become like the middle class. It was a tough and controversial message about changing attitudes, about permissive immorality.

"The lower economic and lower-middle-economic people are not holding up their end of the deal," he famously told the NAACP in 2004 on the 50th anniversary of Brown v. Board of Education, which ordered the desegregation of the public schools. "No longer is a (girl) embarrassed because she's pregnant without a husband," he said. "No longer is a boy considered an embarrassment if he tries to run away from being the (unmarried) father of the child."

When he observed that the black teen birthrate is twice that of whites, he was accused of blaming the victim, of talking like an "elitist." But now many prominent blacks, including Barack Obama, echo Bill Cosby. They're speaking out aggressively against gangsta rap, prison fashion chic, foul language against women and the perverse idea that working for good grades is selling out to "the man." But the problems can't be papered over by talk about "change." The bigotry of low expectations is exacerbated when the black working poor are among the hardest hit when jobs disappear and the economy drifts into recession.

The pathway from "victims to victors," as Bill Cosby puts it, is littered with obstacles. Martin Luther King had a wonderful dream. Now comes the wake-up call to put it into action. It won't be easy, but finally it seems possible.