The latest polls suggest that as many as 58 per cent of Americans now support same-sex marriage, compared with just 13 per cent 25 years ago.
It's not just a generation gap that explains the profound shift, pollsters are discovering — even some older Americans are changing their minds about gay marriage, as are citizens in rural areas, from religious backgrounds and in traditionally conservative jurisdictions.
Amid that backdrop, the nine-member Supreme Court will hear arguments Tuesday in a challenge to California's Proposition 8, a 2008 state referendum that defined marriage as an institution between a man and woman. Prop 8 has served to outlaw same-sex unions in the otherwise liberal state.
Aja Aguirre — who married her partner in San Francisco in 2008, just before Prop 8 passed — says their battles have been nothing compared to other couples who have spent decades fighting for basic rights in several states.
The couple moved to Massachusetts last year, purposely choosing to transfer to a state that recognizes same-sex marriage.
Prop 8 "has been a battle that's lasted as long as our marriage, and that's sobering," Aguirre, 32, said in an interview from Boston.
"Following and fighting has, at times, felt like a kind of emotional abuse. You invest time and energy and money where you can, you hope — you triumph, even — and then just as you start to get up and dust yourself off, you get kicked down again."
A day after the Supreme Court weighs Prop 8, it will hear arguments on the Defense of Marriage Act, legislation that denies federal benefits to spouses in gay marriages and prevents the federal government from recognizing same-sex unions in states where they are legal.
That act was signed into law by former president Bill Clinton, who recently admitted that he regrets the decision.
The challenge to the legislation known as DOMA was spearheaded by 83-year-old Edith Windsor. The New Yorker married her longtime partner Thea Spyer six years ago in Canada, where same-sex marriage has been legal for almost a decade. The couple's marriage was recognized by New York's state government.
But when Spyer died in 2009, the federal government cited the Defence of Marriage Act to force Windsor, who's now ailing, to pay $363,000 in taxes on her late wife's estate — taxes that wouldn't have been levied against her if she'd been married to a man.
"It's heartbreaking," Windsor said in a recent interview. "It's just a terrible injustice, and I don't expect that from my country. I think it's a mistake that has to get corrected."
The arguments, made before the Supreme Court panel of five Republican appointees and four Democrats, will be heard even as some high-profile Republicans, long consumed with winning over the social conservatives of their base, express support for same-sex marriage.
Ohio Sen. Rob Portman recently reversed his stance after his college-age son revealed he was gay. Jon Huntsman, a Mormon and a Republican presidential candidate in 2012, has also backed same-sex marriage and urged his fellow Republicans to do the same.
Even Karl Rove, the powerful Republican strategist who famously brought millions of Christian evangelicals into the party fold a decade ago, says he wouldn't be surprised if the 2016 Republican presidential candidate — whoever that may be — backs same-sex marriage.
U.S. President Barack Obama has helped embolden fellow politicians on same-sex matrimony after he reversed his own stance on the issue last year, becoming the first commander-in-chief in American history to back gay marriage. The White House is also urging the high court to rule in favour of same-sex rights.
In recent weeks, Hillary Clinton, eyeing a run for president in 2016, has expressed her support. Congressional Democrats are also beginning to claim the issue as their own as the 2014 mid-term elections loom on the horizon.
A brief filed by Democratic lawmakers to the Supreme Court urging it to overturn the Defence of Marriage Act sounded an apologetic tone as it made note of society's rapidly changing attitudes about same-sex marriage. That's despite the fact that many of them voted in favour of the act in 1996.
"In short, it was a different world for gay men and lesbians, and many were understandably reluctant to speak openly about themselves or their families," said the brief, signed by more than 200 sitting congressional Democrats.
"A number of members, like the constituents we serve, did not personally know many (if any) people who were openly gay and majority attitudes toward that minority group were often viscerally fearful and negative."
The high court will rule on the cases some time in June.
Legal experts say Justice Anthony Kennedy, a libertarian conservative on the panel, is the judge to watch this week. Kennedy has already written two judgments for the court that upheld the rights of gays.
John Roberts, the chief justice of the Supreme Court who infuriated conservatives last year by voting in favour of Obama's sweeping health-care reform law, could anger them anew in 2013 — especially since his gay cousin will be in D.C. this week to hear the arguments.
Jean Podrasky told the Los Angeles Times that she will be sitting in a section reserved for Roberts’s guests during the Prop 8 hearing on Tuesday. Podrasky, 48, wants to marry her partner of four years, Grace Fasano, who will also be in attendance.
Podrasky, a San Francisco resident, said she has no personal knowledge of Roberts’ position on the issue, but is optimistic.
“He is a smart man,” Podrasky said of her cousin, appointed to the court by George W. Bush in 2005. “He is a good man. I believe he sees where the tide is going. I do trust him. I absolutely trust that he will go in a good direction.”