The US Supreme Court is hearing two cases critical to the rights of gay couples to marry.
Public opinion on the topic of gay and lesbian rights in the United States, a politically dangerous issue not long ago, has undergone one of the most rapid evolutions in recent history.
According to a Pew Research Centre poll conducted in mid-March, 49% of Americans now favour allowing gays and lesbians to marry legally, with 44% opposed. A decade ago the numbers were heavily tilted in the opposite direction: 58% opposed and just 33% in favour.
But the shift does not guarantee an outcome in favour of gay marriage in the conservative-leaning court. Lawyers representing two couples from California will try to persuade the nine Supreme Court justices to strike down the state's voter-approved ban on same-sex marriages and to declare that gay couples can marry nationwide.
Lawyers representing supporters of the California ban known as Proposition 8 will argue that the court should not override the democratic process and impose a judicial solution that would redefine marriage in the some 40 states that do not allow same-sex couples to wed.
The case, having wound its way to the high court, could produce a number of rulings, ranging from upholding the California ban to striking it down in a fashion that would erase such bans nationwide. The court is not expected to rule before late June.
Nine states and the district of Washington allow same-sex marriage, 12 others recognise "civil unions" or "domestic partnerships" that grant the same benefits without full rights of marriage. The 29 other states ban gay marriage in their constitutions.
The court is also to hear the first challenge it has accepted to the Defence of Marriage Act, the 1996 measure signed into law by former president Bill Clinton. Both he and his wife, potential 2016 Democratic presidential candidate Hillary Clinton, recently reversed course and now support same-sex marriage. The law, known as DOMA, forbids nationwide recognition of same-sex marriages and bars married gay and lesbian couples from receiving federal benefits.