In post-Great Recession America, which is the bigger barrier to opportunity — race or class?

A decade ago, the U.S. Supreme Court kept the focus on race as a barrier, upholding the right of colleges to make limited use of racial preferences to ensure a diverse student body. But in a ruling due this month, the court is widely expected to roll back that decision. Such an outcome would shift attention more toward a less constitutionally controversial practice: giving a boost to socio-economically disadvantaged students, regardless of race.

If that happens, it would reflect more than just a more conservative makeup of the justices. In the past decade, clogged social mobility and rising economic inequality have shifted the conversation on campuses and in the country as a whole.

As a barrier to opportunity, class is getting more attention, while race is fading.

“The cultural zeitgeist has changed,” said Peter Sacks, author of the book “Tearing Down the Gates: Confronting the Class Divide in American Education.”

“The Great Recession really exacerbated the vast and growing inequalities between rich and poor in America,” he said. “Talking openly about class has been taboo,” he added, but in recent years the evidence of widening inequality has mounted and it’s become “OK for the so-called 99 percent to talk about the 99 percent.”

The shift is perceptible in surveys from the Pew Research Center that show the percentage of Americans who feel racial discrimination is the chief impediment to black progress is falling, from 37 percent in 1995 to 23 percent in 2012. Polling on affirmative action varies widely depending on how questions are phrased, but an ABC News/Washington Post poll released Wednesday showed strong feelings about using race in college admissions: Just 22 percent of Americans support letting universities consider applicants’ race as a factor, and 76 percent oppose the practice. The proportions supporting racial preferences were similar for blacks (19 percent) and Hispanics (29 percent) as for whites (20 percent).

The shifting debate has painted supporters of race-based affirmative action into a difficult corner. Most agree the barriers to low-income students are a serious problem that should be addressed, and of course, many minority students are also low-income. But they acknowledge widening income inequality has made it harder to make their case that special attention to race remains justified.

“This is the first time you have whites thinking they face more discrimination than blacks do,” said Camille Charles, a sociologist at the University of Pennsylvania who studies class and race. “You have people who have come to believe the system is set up to benefit black people at the expense of white people.”

In his 2010 book “The Moral Consequences of Economic Growth,” Harvard economic historian Benjamin Friedman charted how during periods of prosperity, societies throughout history have expanded opportunities to disadvantaged groups and become more open and inclusive. During economic struggle, by contrast, they typically close ranks.

The Great Recession was no exception, he said, persuading more Americans that efforts to ensure minorities are represented among the scarce slots at top universities are “a luxury they cannot afford,” Friedman said by telephone.

On college campuses, arguments over race and gender have predominated for decades, but the lack of socio-economic diversity is getting more attention. One sign of the trend is the emergence of a student group called “U/FUSED” (United for Undergraduate Socio-Economic Diversity), with chapters on about 20 prominent campuses. Chapters at campuses like Wesleyan University and Washington University in St. Louis have undertaken a range of efforts, from developing a financial literacy curriculum to lobbying for more financial aid.

But mostly, said Chase Sackett, who helped found the organization while an undergraduate at Washington University and is now a law student at Yale, the groups are getting people to talk about the previously taboo subjects of class, money and inequality.

College students are actually fairly accustomed to talking about race, he said, but class “was something that was under the rug.” He said minority groups have been eager to join the conversation, seeing it as complementary to the issues they care about.

Sackett said he and the group don’t necessarily oppose race-based affirmative action; they just want more efforts to deal with socio-economic diversity.

“Low-income will not replace diversity,” said Ted Spencer, admissions director at the University of Michigan, which won the right to use race as an admissions factor in the 2003 Supreme Court case but later lost it in a voter referendum. Michigan’s numbers of minority students have not fully recovered.

But Spencer emphasized the court’s justification for race-based affirmative action has never been only about minorities, or about rectifying society-wide discrimination, or about pitting racial barriers against class ones.

Rather, the court’s justification was educational — that all students benefit from a racially diverse student body. Employers increasingly want students accustomed to working with people from different groups, and many students want that experience, too. If the court rules as expected, he’s worried they’ll have few options.

“As we prepare people for work and life,” he said, “the absence of diversity on campus deprives all of our students of a very important part of their academic growth.”