The Supreme Court last week heard oral arguments on both a challenge of the Defense of Marriage Act (DOMA), which bars the government from distributing certain spousal benefits to same-sex couples, and a California ballot initiative that banned gay marriage in the state. Gay-rights activists hope a favorable ruling could strike down prohibitions on same-sex marriage across the United States.
Casey's decision means now just seven of the 53 Democrats in the Senate do not support gay marriage. But every Republican senator except Ohio's Rob Portman — who said last month that his gay son had led him to change his mind — opposes same-sex marriages.
Carper had previously said he believed that DOMA should be repealed, but said that same-sex marriages should be left up to the states.