So it's worth recalling that these policies have lasted as long as they have because of compromises - in which Republicans played a crucial part.
In 1977, white applicant Allan Bakke asked the Supreme Court to strike down a University of California program that awarded a fixed number of spots in medical school to African Americans and other historically disadvantaged minorities. Justice Lewis Powell, a Richard Nixon appointee, crafted an opinion that forbade quotas while permitting schools to take race into account for the sake of "diversity."
Powell's amorphous rule satisfied neither civil rights advocates, who saw quotas as compensation for past discrimination, nor critics, to whom any use of race is "reverse discrimination." But it proved workable - increasingly so as prosperity lessened students' sense that college admissions are a zero-sum contest.
Asked to overturn the ruling in 2003, the court sustained it; Sandra Day O'Connor, whom Ronald Reagan appointed to replace Powell, wrote the key opinion.
In 1982, Congress considered an extension of the 1965 Voting Rights Act. The debate pitted a rising conservative movement against liberal civil rights organizations. To oversimplify somewhat, the question was whether to regulate state practices that resulted not only in fewer minorities voting, but also in fewer being elected.
Congress approved a Powell-like standard, barring proportional representation but taking account of "the extent to which members of the minority group have been elected to public office in the jurisdiction." The architect of the compromise was then-Sen. Robert Dole, Republican of Kansas. Reagan signed it into law.
Subsequent history has shown the benefits and defects of each compromise.
Between 1976 and 2010, the African American share of college enrollment rose from 9.4 percent to 14.5 percent, according to federal data. The number of black elected officials rose ninefold between 1970 and 2000. This is revolutionary.
Still, using race as "one factor" has often become a euphemism for using it as the decisive factor. That understandably rubs many Americans the wrong way, especially in a multiethnic society that resembles the old white-black caste system less and less. And access is not the same as success: African American college students graduate at about half the rate of whites.
Race-conscious gerrymandering arguably fuels polarization, encouraging the parties to split voters into white and minority districts and pitch them mutually exclusive policies. It's not clear whether minorities have more power as a dominant group in a noncompetitive district or as a swing vote in a competitive one.
It's in the nature of litigation for each side in these cases to play down such nuances. Each wants the court to rule unequivocally in its favor - and to resolve the vexed questions once and for all.
I would agree if I were confident that the rights and wrongs could be so readily defined. But I'm not. Half a century after Selma, and 35 years after Bakke, we still need practicality and compromise. We need the realism, and wisdom, of Powell, O'Connor, and Dole.
Charles Lane is an editorial writer for the Washington Post.