“People feel that there’s something callous, something racially indifferent in saying, ‘Wait a minute; we’ve come a long way,’ ” said Ms. Thernstrom, a longtime critic of affirmative action who is a senior fellow at the Manhattan Institute, a conservative research group.

“But whether he wins or loses, for a black man to become a standard-bearer for one of the two major parties, it does say something,” she said. “It says that the road we started down in 1965 with the Voting Rights Act has come to an end. We don’t need to talk about disfranchisement in the same way anymore.”

The fortunes of black Americans have certainly improved since the civil rights struggle of the 1960s. The number of educated, professional blacks has grown as poverty rates have declined. About 17 percent of blacks held bachelor’s degrees in 2004, compared with 5 percent in 1970, census data shows. (About 30 percent of whites held bachelor’s degrees that year.) In 2005, college-educated black women who worked full time earned more than their white female counterparts, census data shows.

But significant gaps between blacks and whites remain. About a quarter of blacks lived below the poverty line in 2006, compared with 8 percent of whites, census data shows. The median income of blacks, $30,200, is less than two-thirds that of whites, $48,800. And studies suggest that employers often favor white job seekers over black applicants, even when their educational backgrounds and work experiences are nearly identical.

Such disparities might explain the differences in opinion that remain between blacks and whites.

In a New York Times/CBS News poll released last month, 53 percent of whites said that blacks and whites had about an equal chance of getting ahead in society. Only 30 percent of blacks agreed.

Blacks and whites were similarly divided over the state of race relations. Fifty-five percent of whites said race relations were generally good, compared with 29 percent of blacks. Nearly 60 percent of blacks said race relations were generally bad.

“A few of my white friends have asked me, ‘With Barack achieving all of this, will we be in a position where we can put race aside?’ ” said Representative Elijah E. Cummings, Democrat of Maryland, who is a co-chairman of Mr. Obama’s campaign in that state.