The Supreme Court issued a qualified but resounding endorsement of affirmative action in higher education yesterday, in a pair of decisions that, taken together, ratified diversity as a rationale for race-conscious admissions and laid out constitutionally acceptable means for achieving it.

A 5 to 4 majority upheld the University of Michigan law school's approach to enrolling a "critical mass" of blacks, Latinos and Native Americans, under which the school considers each applicant individually and sets no explicit quota. At the same time, a 6 to 3 majority rejected as too mechanistic Michigan's undergraduate affirmative action program, which gives members of these "underrepresented" groups an automatic 20-point bonus on the 150-point scale used to rank applicants.

The net effect of the two rulings was to permit public and private universities to continue using race as a "plus factor" in evaluating potential students -- provided they take sufficient care to evaluate individually each applicant's ability to contribute to a diverse student body. A majority also endorsed the view that diversity-based affirmative action should not be a permanent feature of American life, urging universities to start preparing for the day when, 25 years hence, the court suggested, it should no longer be necessary.

It was 25 years ago that the court, in its splintered decision in Regents of the University of California v. Bakke, ruled out racial quotas but left the door open to the consideration of race in admissions. Yesterday's rulings reaffirmed that basic conclusion, and amplified the conditions under which race can be considered.

At the center of the action was Justice Sandra Day O'Connor, often a centrist swing voter on the court, who voted with the majority on all the key holdings of yesterday's cases.

It was O'Connor who, in a firm voice, announced the court's crucial opinion in the law school case, describing for a hushed audience the social and educational benefits of racial and ethnic heterogeneity on the campuses of America's selective institutions.

"Effective participation by members of all racial and ethnic groups in the civic life of our Nation is essential if the dream of one Nation, indivisible, is to be realized," O'Connor wrote, in an opinion joined by Justices John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer.

"Moreover, universities, and, in particular, law schools, represent the training ground for a large number of our Nation's leaders," she wrote. "In order to cultivate a set of leaders with legitimacy in the eyes of the citizenry, it is necessary that the path to leadership be visibly open to talented and qualified individuals of every race and ethnicity."

Yet, she added, to be consistent with the constitutional guarantee of equal treatment for all under the law, "race-conscious admissions must be limited in time." Specifically, O'Connor wrote, "We expect that 25 years from now the use of racial preferences will no longer be necessary."

Chief Justice William H. Rehnquist, in a dissenting opinion joined by Justices Antonin Scalia, Clarence Thomas and Anthony M. Kennedy, denounced the law school admissions plan as a "sham" and a "naked effort to achieve racial balancing." Blacks, Latinos and Native Americans are actually admitted in rough proportion to their presence in the applicant pool, Rehnquist noted, attributing this to "a carefully managed program designed to ensure proportionate representation of applicants from selected minority groups."

Supporters of affirmative action, who had been bracing for the possibility that the court could strike down both programs, were jubilant. While narrowing the options for affirmative action somewhat and projecting an end to it within a generation, the court had nevertheless preserved the essence of a concept that receives mixed reviews in public opinion polls but to which the country's business, education and military leaders have become deeply committed.

"This is a tremendous victory for the University of Michigan, for all of higher education, and for the hundreds of groups and individuals who supported us. A majority of the court has firmly endorsed the principle of diversity," the university's president, Mary Sue Coleman, said in a statement. "The court has provided two important signals. The first is a green light to pursue diversity in the college classroom. The second is a road map to get us there."

Officials at the Center for Individual Rights, the public interest law firm that has been waging court battles against affirmative action in higher education for most of the past decade, conceded that they had fallen short of their goals, but said they might pursue new lawsuits if universities stray from the court's new rules.

"It's a pretty fine line they have to walk," said CIR spokesman Curt Levey. "They would be well-advised to follow the court's suggestion to move as quickly as possible to race-neutral policies."

The affirmative action debate has raged not only around ballot boxes, on TV talk shows and on college campuses, but also within the halls of government -- most recently as conservatives and moderates within the Bush administration engaged in a fierce internal struggle over how to respond to the Michigan cases without alienating either the Republican Party's traditional conservative base or potential minority supporters, especially Latinos.

Ultimately, the administration straddled the issue, arguing in a friend-of-the-court brief that racial and ethnic diversity are important goals, but that both the undergraduate and law school programs were unconstitutional because the university had failed to attempt race-neutral means of achieving diversity first.

The administration endorsed instead "10 percent" plans, such as Texas's guarantee of admission to the University of Texas to students in the top 10 percent of each high school class in the state.

O'Connor's opinion devoted relatively little time to the administration's views. She noted that "10 percent" plans were of little relevance since they could not be easily applied to graduate and professional schools, and added that schools are not required to exhaust "every conceivable race-neutral alternative."

Still, in urging universities to prepare for the day 25 years hence when racial preferences may be phased out, O'Connor did suggest that schools should learn from the experience of states such as California, Florida and Washington, where race-conscious admissions have been abolished.

Declaring a measure of victory, President Bush issued a statement praising the court for its "careful balance between the goal of campus diversity and the fundamental principle of equal treatment under the law. . . . Like the court I look forward to the day when America will truly be a colorblind society."

Seemingly more influential than the Bush administration's views were briefs filed by large U.S. corporations and by former military officials, each of which urged the court to uphold some form of affirmative action.

The businesses argued that a culturally diverse, well-educated workforce is vital to the competitiveness of the U.S. economy. The military leaders, including Desert Storm commander Gen. H. Norman Schwarzkopf, told the court that military cohesion, and, hence, national security hinged on an integrated officer corps produced by diverse military academies and ROTC programs.

Declining to second-guess these prominent figures, O'Connor in the law school case cited their views to support the proposition that the benefits of a diverse student body are "substantial."

And O'Connor drew heavily on the opinion of her friend and former court colleague, the late justice Lewis F. Powell Jr., who wrote the lone opinion in Bakke that first sketched out the diversity rationale for race-conscious admissions.

O'Connor sought to anchor yesterday's rulings in Powell's Bakke opinion, which had been treated as precedent by universities but has never been declared binding by the court itself. O'Connor, too, sidestepped the question of whether Powell's opinion has been law for the past 25 years, declaring instead that the court endorses it now.

She cited Powell as authority both for the holding that diversity can be a "compelling state interest" capable of trumping the Constitution's usual ban on racial classifications by government, and for the holding that the law school's methods of reviewing individual applicants -- which she described as "highly individualized" and "holistic" -- are "narrowly tailored" to meet that interest. It was crucial, she wrote, that under the law school's approach, a nonminority student with a particularly interesting contribution to make to the law school's academic climate may sometimes beat out a minority student with better grades and test scores.

Conversely, O'Connor wrote that the undergraduate program's 20-point bonus ran afoul of the standards for individualized consideration set forth by Powell.

Justice Kennedy, in a dissenting opinion, indicated that he agreed with the majority in the law school case that diversity could justify the use of race in admissions, but disagreed that the law school had indeed found a constitutionally acceptable way of considering it.

O'Connor joined Rehnquist, Scalia, Thomas and Kennedy, plus Breyer, in voting against the undergraduate admissions policy. Stevens, Souter and Ginsburg dissented, with Stevens and Souter arguing that the case should have been dismissed on procedural grounds, and Ginsburg and Souter expressing support for the admissions policy on the merits.

Thomas, the court's only black member and a longtime opponent of affirmative action, wrote a strongly worded dissent in the law school case in which he repeatedly accused the majority of lacking the "courage" to overturn race-conscious admissions.

Thomas argued that Michigan's true interest in the case was not the educational benefits of diversity, but rather pursuing an "aesthetic" of racial mixing while preserving its status as an elite, selective law school.

Thomas pointedly contrasted the majority's deference to the Michigan faculty's assertions that it cannot give up pursuing diversity through race-conscious admissions with the court's 1996 decision to overturn male-only education at the Virginia Military Institute, despite protests by VMI that the changes would be too radical.

"Apparently where the status quo being defended is that of the elite establishment -- here the Law School -- rather than a less fashionable Southern military institution, the Court will defer without serious inquiry and without regard to the applicable legal standard," Thomas wrote.

Yet Thomas and Scalia joined in endorsing one part of O'Connor's opinion: her declaration "that race-conscious admissions must be limited in time." Specifically, O'Connor wrote, "We expect that 25 years from now" -- the same length of time that has elapsed since Bakke -- "the use of racial preferences will no longer be necessary."

This supplied an additional two votes for a proposition about which Ginsburg, in a separate concurring opinion in the law school case that was joined by Breyer, formulated her own distinct view.

Emphasizing the obstacles to minority educational achievement that still remain, Ginsburg wrote that "one may hope, but not firmly forecast, that over the next generation's span, progress toward nondiscrimination and genuinely equal opportunity will make it safe to sunset affirmative action."

At issue in yesterday's cases were claims by prospective students who said they were rejected by the University of Michigan's undergraduate program and law school while minorities with lower grades and test scores were admitted.

The first case was brought by Jennifer Gratz and Patrick Hamacher, who were denied admission as undergraduates in 1995 and 1997, respectively. The second case was brought by Barbara Grutter against Michigan's law school.

One U.S. district judge in Michigan upheld the undergraduate program, and another struck down the law school program.

The cases were appealed to the Cincinnati-based U.S. Court of Appeals for the 6th Circuit. In May 2002, that court, bitterly divided, ruled 5 to 4 that the law school program was constitutional based on Powell's opinion in Bakke. That ruling differed from rulings by federal appeals courts in New Orleans and Atlanta and coincided with one by a San Francisco-based appeals court.

As a result of this disagreement, lawyers from the Center for Individual Rights appealed the law school case to the Supreme Court. But because the 6th Circuit never issued a ruling on the undergraduate case, they also asked the justices to hear it under a special provision of Supreme Court rules.

Michigan objected to the Supreme Court hearing either case but told the court that if it agreed to hear the law school case, it should hear the undergraduate case because they are so closely related. The cases are Grutter v. Bollinger, No. 02-241, and Gratz v. Bollinger, No. 02-516.

Jackie Bray, far left, of Ridgewood, N.J., and Michelle Lin of Atlanta hug on the University of Michigan campus in Ann Arbor after receiving word of the Supreme Court's decisions that partly uphold the university's programs. Bray is a senior at Michigan and Lin recently graduated.From left, University of Michigan students Madelina Young of Buffalo, Carolina Saenz of Washington, D.C., Patricia Dyer of Birmingham, Ala., and Jane Rhee of Tucson chant during a rally on the Ann Arbor campus to celebrate the Supreme Court's decision.The court ruled in favor of Jennifer Gratz, above, who was rejected by Michigan when it had system of awarding points to minority applicants.The court's opinion in Grutter is a "green light" to pursue diversity, said University of Michigan President Mary Sue Coleman.