The way American opinion and expectations are evolving, it's unlikely anyone will get elected president in 2016 standing in the way of same-sex marriage.
While some candidates hold their ground, promising to pursue a constitutional amendment banning same-sex marriage if the Supreme Court upholds recognition of it in rulings expected this month, the movement in support is simply tectonic.
Just 10 years ago, 53 percent of Americans surveyed opposed marriages of men and the wedding of women and just 36 percent supported such matrimony, the Pew Research Center has found. In the latest Pew poll reported this week, the numbers had shifted to 57-percent support and 39-percent opposition in May.
And perhaps most remarkably -- while nearly two-thirds of Democrats support same-sex marriage and only one-third of Republicans do -- there is no partisan divide whatsoever on the question of whether it is inevitable that American law will recognize these marriages: 72 percent of Democrats and Republicans say so.
"The American public has changed,'' says Andrew Kohut, founding director of the Pew Center, looking at the strongest support for same-sex marriage registering among "millennials'' born since 1980. "A lot of it is generational change on these issues... The younger generations are leading the charge."
As dramatic as the shift in opinion on this question may be, it's not unique. The Gallup Poll, in business for a long time, has charted American attitudes about marriages between whites and blacks. Support stood at just 4 percent in 1958. It stood at 87 percent by 2013. From 1995 to 2013 alone, it rose from 48 percent.
Kohut points also to his own center's surveys on American values since the late 1980s. Belief that government is run for the benefit of the people has fallen from 60 percent in 1987 to 40 percent in 2012. And any agreement that women should return to ``traditional roles'' in American life has shrunk from 30 to 9 percent.
"There are a lot of social issues and basic political beliefs that mirror what we're seeing on gay marriage,'' Kohut says in an interview.
Yet no issue has come to the fore as quickly during the past several years of state constitutional amendments and federal court rulings opening the way for gay marriage. Among millennials, Pew pegs support at 73 percent. Among "Gen-Xers" ages 35-50, support runs at 59 percent. Baby Boomers remain divided.
It's already legal in 36 states and the District of Columbia. Now the high court, which already cast aside some barriers two years ago, is considering two more questions: Whether the Constitution requires states to issue marriage licenses to same-sex couples and, if not, whether the remaining resistant states must recognize these marriages performed in other states where they are legal.
Certainly there's no single social issue that drives a presidential election. Yet just over a majority of adults surveyed say the issue of same-sex marriage is important to them -- 30 percent very important. And given a choice of two candidates, it's not difficult to predict where the millennials and Gen-Xers will turn. They backed President Barack Obama in his elections.
The "Republican presidential choir'' of 2016 is singing a familiar song -- "Yesterday" -- Hillary Clinton said in a Saturday address on New York's Roosevelt Island billed as the first major address of her campaign. "They turn their backs on gay people who love each other.'
The court could do the Republican Party a couple of favors by finding a constitutional right to same-sex marriage -- particularly if the reasoning is based on a more basic question of equal protection of rights for men and women. One result: Stoking the party's religious right. Another result: Offering moderate leaders an invitation to talk about other issues.
"It may give GOP candidates some comfort to not have to address that issue,'' says Carl Tobias, a law professor at the University of Richmond. "The debate will still go on, but it may just be that people need to reconcile themselves to this.''
"The shift in public opinion is compelling, how strong it is and how quickly it happened,'' Tobias notes, pointing to his own law students who ask what the big deal is. "There is more acceptance, and that's just the way it is. I would like this to not be a fight that goes in, if possible, just because I don't see any value in that. I'm hoping whatever they do will not allow this to go on.''
The ruling could give candidates courting the party's base, such as Texas Senator Ted Cruz or Wisconsin Governor Scott Walker, a rallying cry to turn out evangelical Christian voters in the early party caucuses and primary elections. And it could give a more moderate candidate, such as former Florida Governor Jeb Bush, the room he needs to navigate an issue that divides their party -- suggesting, as Bush has before, that the courts are having their say, it's time to move on and, no matter what anyone thinks about the question, everyone deserves respect.
"The people should decide the issue of marriage, not the courts," Cruz has said. "The union of a man and a woman has been the building block of society since the dawn of history, and the people in numerous states have repeatedly affirmed that truth in their laws. Nothing in the Constitution prohibits that."
"If the court decides that" same-sex marriage is supported by the Constitution, Walker said on ABC News' This Week, "the only next approach is for those who are supporters of marriage being defined as between one man and one woman is ultimately to consider pursuing a constitutional amendment.''
This sort of talk goes a long way in Iowa's premier party caucuses.
Mike Huckabee, the former Arkansas governor and Baptist preacher who won Iowa's Republican caucuses in 2008, has contended that marriage for same-sex couples could undo Christianity. "Christian convictions are under attack as never before," Huckabee said in a recent conference call organized by the Family Research Council. "Not just in our lifetime, but ever before in the history of this great republic. We are moving rapidly toward the criminalization of Christianity."
Rick Santorum, the former Pennsylvania senator who narrowly won his party's Iowa caucuses in 2012, said on NBC's Meet the Press that he'd fight a court ruling upholding same-sex marriage. "Roe versus Wade was decided 30 some years ago, and I continue to fight that, because I think the court got it wrong,'' he said. "And I think if the court decides this case in error, I will continue to fight, as we have on the issue of life ... We're not bound by what nine people say in perpetuity."
One of the nine justices -- the one widely considered the swing vote on the same-sex marriage questions -- was offering his own mixed sentiments as he questioned lawyers in the oral arguments over the cases in April.
Same-sex couples are seeking the same "dignity" and "ennoblement" as heterosexual couples, Justice Anthony Kennedy said. He also said that the definition of marriage as between a man and woman "has been with us for millennia. And it's very difficult for the Supreme Court to say, 'Oh, well, we know better.'"
Chief Justice John Roberts Jr. also echoed one of the questions posed in writing in briefs presented to the court when he asked: "If Sue loves Joe and Tom loves Joe, Sue can marry him and Tom can't. Why isn't that a straightforward question of sexual discrimination?"
Donald Verrilli, the Obama administration's solicitor general, likes the equal-protection case. "Gay and lesbian people are equal,'' he told the court, "they deserve equal protection of the law and they deserve it now."
Obama made his own personal support for same-sex marriage known as he was preparing his campaign for re-election in 2012. Opposition was a losing question within his own party, a potential point of alienation for the younger voters who helped put him in the White House. He had struggled to dodge addressing "a particularly nagging issue,'' adviser David Axelrod wrote in his book, Believer. "I'm just not very good at bullshitting,'' Obama told Axelrod, the writer says.
Opposition was a losing proposition for Republican rival Mitt Romney, though certainly not the biggest factor in his defeat. Hillary Clinton made her support clear as she left her post as secretary of state in 2013. And one of her 2016 rivals, former Maryland Governor Martin O'Malley, signed the 2012 law that enabled gay men and lesbians to marry in his state.
For Republicans hoping to moderate their tone this time around, Kentucky Senator Rand Paul has offered a Libertarian model. While he maintains that he believes in "traditional marriage,'' he acknowledges differing views and suggests that states can decide their own laws.
But it was Bush who gave the clearest signal earlier this year that he would not allow his own longstanding personal support for traditional values to stand in the way of his bid for the White House, to be formally announced next week.
"We live in a democracy, and regardless of our disagreements, we have to respect the rule of law,'' Bush said in a statement issued in January. "I hope that we can also show respect for the good people on all sides of the gay and lesbian marriage issue -- including couples making lifetime commitments to each other who are seeking greater legal protections and those of us who believe marriage is a sacrament and want to safeguard religious liberty."