But even without federal intervention, a look at affirmative action policies in 2017 shows that they have achieved their own kind of diversity, evolving from the explicitly race-based quotas of decades ago into a range of approaches that occasionally, not always, near the melting-pot ideal, often by giving preference to low-income students instead of minorities.

“The reason a liberal like me is intrigued by Trump’s actions on affirmative action is that I think it could have the effect of driving universities to really pursuing socioeconomic diversity as a way of indirectly creating racial diversity,” said Richard D. Kahlenberg, a senior fellow at the Century Foundation who has pushed for class-based admissions to replace race-based admissions.

Public universities in California and Washington, forbidden by state law from considering race in individual admissions decisions, have attempted to use socioeconomic factors as a substitute, hoping to draw from the overlap of minority and low-income students. Others, like the University of Texas, accept a set percentage of the top students at every state high school. Neither method has fully succeeded in composing student bodies that match the racial makeup of their states.

Other colleges with more freedom to curate a student body continue to weigh race as one factor in admissions, which can lead to more diversity. But their decision-making can be so subjective that, in the minds of high school seniors staring down application season, it can border on the occult.

It is this opacity that has left few happy: not Asian-American students who feel that they are being held to a higher standard, and whose complaint against Harvard has become a focus of the Justice Department’s efforts; not white students who feel similarly penalized; and not those who remain the theoretical face of affirmative action, African-American and Latino applicants who say the assumption that their success depended on their race can shadow them far beyond commencement.