History Cometh: Supreme Court to Rule on Gay Marriage

It's a day for the history books: Two landmark Supreme Court rulings on gay marriage are coming today, something we know with certainty because it's the last day of the term. The justices will convene at 10am ET and issue their rulings shortly thereafter, reports the New York Times. A quick primer on what to expect:

• One case: DOMA. DOMA defines marriage as a union between one man and one woman, meaning that gay couples who legally wed in states that allow gay marriage are denied federal benefits. The high court must decide if the federal government can constitutionally do that. (More on the lesbian couple the case involves here.)
• What could happen here: If DOMA is struck down, the federal benefits would start flowing to affected couples; if it's upheld, things will remain as they are. The court could also punt by saying that House Republicans do not have the standing to defend the law in the first place. The court sounded pretty skeptical during its oral arguments on the case three months ago, with SCOTUSBlog putting the chance of DOMA's demise at 80%.

• Second case, Prop 8: California's voter-approved Prop 8 banned same-sex marriage after the state Supreme Court allowed it. A federal district judge struck down Prop 8, but his decision was stayed until the Supreme Court could weigh in.
• What could happen here: There are more possible outcomes in this case. The court could uphold Prop 8, determine it is powerless to hear the case (more on that here), or strike Prop 8 down. Should the justices go with the third option, their ruling could go one of three ways, as explained here. Most narrowly, such a decision would affect only California. Most broadly, they could deem all bans on gay marriage unconstitutional.
• You may have to wait a few minutes past 10am: The AtlanticWire notes that there's a third ruling coming today, and that'll likely be first in line.
• Today's best sidebar: This Slate piece on how, and why, the Supreme Court schedules its decisions the way it does.
• Interesting side note: The Times observes that when the justices heard arguments in the cases in March, gay marriage was legal in nine states, plus DC. In the months since, three more states have joined that group.

(More US Supreme Court stories.)