The marriage debate has often been difficult, but it also affirms America’s political tolerance and adaptability. The best tradition of U.S. democracy is to mediate controversies, giving all sides a fair hearing. Not everyone will like the results at the ballot box, but at least they can accept them as legitimate.

A same-sex marriage ukase would achieve that rare thing, harming advocates and opponents and everyone in between. Since marriage is more than an intimate relationship but an expression of legitimacy in the eyes of society, Supreme Court-mandated marriages would confer fewer benefits on gays and lesbians than would popular acceptance. Meanwhile, the Court would tell millions of Americans that their deep moral convictions are artifacts of invidious bigotry.

The Supreme Court does not have a good record legislating cultural change. A ruling on behalf of same-sex marriage could enshrine Hollingsworth and Windsor with Roe v. Wade, the 1973 abortion decision that imposed a judicial diktat even as laws in many states were liberalizing. Instead of finding a rough consensus inside the political mainstream, abortion became an all-or-nothing combat that still rages.

The same-sex marriage cases are an opportunity for the Court to show it has learned from that mistake. Justice Kennedy and his colleagues can incite another Forty Years War or they can return their social jurisprudence to the measured, incremental approaches the Constitution intends.