Following the Supreme Court’s landmark decision Friday that same-sex couples have a constitutional right to marriage, several Harvard Law School professors said Justice Anthony M. Kennedy, who authored the majority opinion, played an extraordinary role in advancing the cause.

“The majority opinion by Justice Kennedy was a triumph of reason and passion alike,” Law School professor and former Supreme Court clerk Laurence H. Tribe ’62 wrote in an email.

Shortly after the Supreme Court’s decision earlier this year to hear arguments regarding same-sex marriage, Tribe and several other professors pointed to Kennedy as a potential “swing vote” in the case, predicting the ultimate 5-to-4 vote outcome.

In his majority opinion Friday, Kennedy wrote that states were not permitted to restrict same-sex couples from marriage, establishing a fundamental right to same-sex marriages.

“As some of the petitioners in these cases demonstrate, marriage embodies a love that may endure even past death,” Kennedy wrote in Obergefell v. Hodges. “Their hope is not to be condemned to live in loneliness, excluded from one of civilization’s oldest institutions. They ask for equal dignity in the eyes of the law. The Constitution grants them that right.”

Kennedy, whose opinion drew fiery dissents from the four more conservative justices on the bench, “treated opposing arguments with respect but showed them to be ultimately unconvincing,” Tribe wrote on Friday. “And his reliance on the synergy of liberty and equality, centered on the core principle of human dignity, will become a permanent fixture in America’s jurisprudence.”

Law School professor Michael J. Klarman wrote that Friday’s decision “confirms the extraordinary influence” of Kennedy, adding that he believes Kennedy is “the most powerful justice in history.”

Kennedy has authored landmark gay rights decisions in the past. In a similarly divided decision two years ago, Kennedy wrote for the majority in striking down the Defense of Marriage Act, the federal law that defined marriage as a union between a man and a woman. And in 2003, Kennedy wrote the majority opinion in Lawrence v. Texas, which invalidated state anti-sodomy laws.

Moving forward, professors said they envision little backlash from the public in the political realm.

Klarman wrote that unlike the issues in Supreme Court cases such as Brown v. Board of Education and Roe v. Wade, “gay marriage does not have the sort of direct effects on opponents that those other rulings do,” adding that the Republican party will ultimately benefit from same-sex marriage being off the table.

“The Court’s taking the issue away from them is one of the best things that could happen to the Republican party going into the 2016 presidential election,” Klarman wrote.

Law School professor Richard H. Fallon agreed that people opposed to same-sex marriage may be angry about the verdict, they are unlikely to act politically, given a shift in public support for same-sex marriage in recent years.

—Staff writer Jalin P. Cunningham can be reached at jalincunningham@college.harvard.edu. Follow her on Twitter @JalinCunningham.