This is the story of Edie and Anthony, two people destined to be together. Edie Windsor, an IBMer with a master's in math, married Dr. Thea Spyer, a clinical psychologist, in 2007 in Toronto after a 40-year engagement.
In '09 Spyer died from MS and left a considerable estate to her longtime love. But Edie got a federal estate tax bill for $363,000 because the Defense of Marriage Act requires the federal government to treat Edie and Thea as strangers. If Thea had been, say, Theodore, the tax bill would've been $0. Edie sued, asking why the federal government treats gay married couples differently. Several lower courts found DOMA unconstitutional. So it was inevitable that before long, Edie (and the freight train that is the gay rights movement) would encounter Anthony (Supreme Court Justice Anthony Kennedy, perhaps the most powerful Supreme of all time because he's the swing vote and is almost always with the majority).
When the Supremes get down to assessing DOMA we can expect the conservatives--Antonin Scalia, Clarence Thomas and Samuel Alito--to defend DOMA, while the liberals--Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan vote to strike it down. So the outcome will be determined by the votes of Chief Justice John Roberts, who's shown he's willing to leave the conservatives if he feels the court's legacy is in peril, and Kennedy, who authored the court's two majority opinions supporting gay rights.
In '96 he wrote the Constitution "prohibits laws singling out a certain class of citizens for disfavored legal status." The Court's other gay rights cause comes from California which gave gays the right to marry and then, with Proposition 8, took it away.
Taking away an existing right because of animus was prohibited by the court in a '96 decision--authored by Kennedy. But where the DOMA case asks, can the federal government discriminate against married couples, the Prop 8 case asks if states can bar gays from marrying.
Here Kennedy has the opportunity to liberate California or create a gay Roe-v-Wade level landmark, opening marriage to all in America. The Supremes know the nation has swiftly grown accepting of marriage equality. Kennedy can only give the gay rights movement a decisive final victory or force the battle to go on a while longer. Ultimate defeat is impossible.
The momentum of the gay rights movement cannot be stopped. Gays will continue coming out and demanding rights and suing for equality until they win. The opposition can only build dams to hold off the inevitable tidal wave of justice because we're taking about something fundamental in society: the right to choose your nuclear family without being penalized. The right to have your relationship respected. Isn't that what the pursuit of happiness is about?