When the Supreme Court last ruled on affirmative action, almost a decade ago, Justice Anthony M. Kennedy issued a 13-page dissent that may now provide the best guide to the future of affirmative action.

Justice Kennedy charted a path between the liberal-leaning ruling that essentially upheld race-based admissions programs and the dissents from his more conservative colleagues, who called for the programs’ abolition. He agreed that universities could take race into account in order to create diverse classes. But he argued that race should be “one modest factor among many others” — and that universities were instead treating it as “a predominant factor,” which was unconstitutional.

In the 10 years since that case, Grutter v. Bollinger, the court has moved to the right. Justice Samuel A. Alito Jr., a critic of affirmative action since the 1980s, has replaced Justice Sandra Day O’Connor, who wrote the majority opinion upholding the practice in 2003. That switch leaves Justice Kennedy as the swing vote in the current case involving the University of Texas, on which the court could rule anytime between next week and late June.