Of the many issues that have fuelled America's culture wars slugfest, same-sex marriage has long been among the most heated.
This week, the heaviest hitter yet will enter the ring, when the US Supreme Court hears oral arguments regarding the legality of two controversial laws barring the practice.
The Defense of Marriage Act (DOMA), passed by Congress and signed into law by President Bill Clinton back in 1996, defines marriage as only between a man and a woman. California's Proposition 8, a ban on same-sex marriage, was passed by popular referendum in 2008.
Also at issue is the difference between civil unions and marriage. Without a recognised, legal standing, same-sex couples are denied a host of federal benefits afforded heterosexual couples.
As such, same-sex marriage advocates say, while civil unions are fine, prohibiting people from marrying is discriminatory.
Roughly 66% of Americans believe that same-sex couples should have the same legal rights as heterosexual couples. Only 30% of people think they shouldn't.
But when it comes to marriage, there is a bit less support – though the number of Americans backing it has grown dramatically in the last decade.
Pollsters at the prestigious Pew Research Center have stated that: "The rise in support for same-sex marriage over the past decade is among the largest changes in opinion on any policy issue over this time period."
According to Pew, in 2003, opponents of same-sex marriage outnumbered supporters by a 58-33% margin. But, in 2013, supporters now have a 49-44% edge.
The poll cited two factors for the change: differing generational views and a change of heart by a sizeable chunk of the population.
All age-groups have seen a spike in support for same-sex marriage since 2003. Among those aged 18 to 49, support has jumped from 41% to 56%. A majority of those over 50 still oppose it, but their majority has shrunk from 65% to 51% in 10 years.
But the writing is really on the wall when considering the younger generation. Among those aged 18-32, support has gone from 51% to 70%.
Whatever the cause of America's shifting attitudes, it doesn't take a rocket scientist to see where the popular opinion train is headed. Politicians, hypersensitive to the direction of political winds, are keenly aware of it.
And, although 31 states have passed laws banning same-sex marriage since 2003, nine states and the District of Columbia have legalised it.
Same-sex marriage advocates clearly have public opinion on their side.
But, at the end of the day, the Supreme Court isn't supposed to care about public opinion. Its remit is to interpret constitutional and legal precedents. And how the court ultimately rules will determine how far same-sex marriage advocates have travelled, or how far they have yet to go.