It’s always risky to put too fine a point on some historical events, but today’s ruling by the U.S. Supreme Court legalizing gay marriage in all 50 states tells me that the court has issued a ruling that is going to change the nation’s landscape … forever.

We can give credit — although some will assess blame — on one justice. That would be Anthony Kennedy, a normally conservative justice who sided with the liberals on the court and wrote the 5-4 majority opinion legalizing gay marriage.

Game, set and match? Not by a long shot.

Kennedy’s role, though, does have an interesting parallel with another justice from another time — with whom he served for five years on the same Supreme Court.

Harry Blackmun was selected to the court in 1971 by a conservative president, Richard Nixon; Kennedy joined the court in 1988 when another conservative president, Ronald Reagan, nominated him.

Blackmun eventually would veer far from where President Nixon thought he’d travel as he served on the highest court in the land. Blackmun became one of the court’s more liberal members.

In January 1973, he authored a landmark ruling that made abortion legal in the United States. Roe v. Wade was a case out of Texas in which the court overturned a Texas law that made getting an abortion a felony offense. Blackmun’s opinion stated that women essentially were entitled to control their own reproductive capacity. The 7-2 ruling set the stage for a debate that hasn’t let up over the course of the past 42 years, but it was a huge decision.

The man on the hot seat now is Kennedy, who remains a conservative jurist. But on this issue, gay marriage, he has decided — along with the court’s liberal wing — that the 14th Amendment to the Constitution, with its equal protection clause, trumps states’ reluctance to allow gay couples to marry.

I doubt strongly we’re going to see Justice Kennedy become a flaming liberal in the wake of this ruling. He just happens to be right — and courageous — in making this decision.

Just as Roe v. Wade changed the landscape in early 1973, today’s ruling on gay marriage sets the stage for another gigantic sea change across the nation.

I wish I was a fly on Justice Kennedy’s wall when he talked this over with his court colleagues and his staff as he pondered how he would write this Earth-shattering opinion. Something tells me he heard the late Justice Blackmun’s voice.