Still, Mr. Payton said, “everybody is nervous that in a political campaign we get reduced to slogans, and the narrowest of slogans, so that you don’t get good discussions.”

In some respects, Mr. Obama’s remarks simply reflect a growing consensus that class should play a significant role in affirmative action programs. It already does in states like California and Michigan, where voters have decided that race can no longer be a factor in government hiring or public university admissions. A Supreme Court decision last year, which barred public school districts from assigning students to schools based on their race, has also forced administrators to focus on socioeconomic status in their efforts to integrate segregated public schools.

But the Supreme Court has also said that universities could consider race as they worked to diversify their campuses. Proponents of such programs point out that blacks continue to face discrimination regardless of class or income. Some fear that Mr. Obama’s focus on the socioeconomic status of his daughters  as opposed to the diversity of experience and perspective they might bring to predominantly white campuses  may help conservatives in their battle to eliminate race from university admissions and government hiring.

Ward Connerly, a crusader against affirmative action, said he believed that Mr. Obama’s remarks would buoy support for his ballot initiatives in Arizona, Colorado and Nebraska in November that would ban preferential treatment on the basis of race, ethnicity and sex in government hiring and public education.

Last week, Mr. Obama’s Republican rival, Senator John McCain, announced his support for those measures. He also accused Mr. Obama of injecting race into the campaign, citing his remarks that Republicans would try to scare voters by pointing out that “he doesn’t look like all those other presidents on the dollar bills.” Mr. Obama’s campaign officials said the remark had been misconstrued.

Mr. Obama opposes the ballot initiatives, saying they would derail efforts to break down barriers for women and members of minorities. But Mr. Connerly said Mr. Obama had already helped the cause. “He’s advanced the debate,” Mr. Connerly said. “He’s brought it to a new level.”

Charles J. Ogletree Jr., a professor at Harvard Law School and an adviser on black issues to Mr. Obama, said some of Mr. Obama’s supporters were “obviously concerned about whether this is a retreat from a commitment to affirmative action in its classical sense.”