The court's make-up of four reliably liberal justices, four reliably conservative justices and Justice Anthony Kennedy, who often wields the deciding vote, also could make a ruling upholding same-sex marriage likely. Kennedy wrote the 2003 majority decision that struck down a Texas sodomy law, Lawrence v. Texas, which effectively made same-sex sexual activity legal in the United States, citing that the law violated the 14th amendment's due process guarantee. A similar argument is being made in the cases working their way forward.
"Kennedy is the wild card. He wrote the decision for the Lawrence case and although there he kind of equivocated a little bit about whether it would also apply in the marriage context, but things have changed now," Silverstein says. "If the composition of the court doesn't change dramatically, I think you see a reasonable possibility of a 5-4 decision in support of same-sex marriage."
Rebekah Metzler is a political writer for U.S. News & World Report. You can contact her at email@example.com or follow her on Twitter.