A slew of recent court victories for gay marriage proponents across the country, including two from federal appeals courts, have amped up speculation the Supreme Court soon will revisit the issue.

Since the Supreme Court last year struck down a key part of the federal Defense of Marriage Act, all of the more than 20 federal and state courts that have addressed the issue have ruled against state bans. Those rulings remain in various stages of appeal.

More than 70 cases have been filed in all 31 states that prohibit same-sex marriage. Nineteen states and the District of Columbia allow such marriages.

The latest decision came Monday, when a federal appeals court in Virginia ruled the state's same-sex marriage ban was unconstitutional.

The ruling had an immediate ripple effect, as North Carolina Attorney General Roy Cooper said hours later that, because of the decision, his office no longer would defend the state's voter-approved ban on same-sex marriage in court.

Because North Carolina is part of the 4th Circuit, Cooper said it was likely the state's ban would be overturned and opposing the lawsuits challenging it would be "futile."

Byron Babione, an attorney for the Alliance Defending Freedom that represented a county clerk sued over the Virginia marriage ban, said his client was considering an appeal. But he added that “ultimately, the question whether the people are free to affirm marriage as a man-woman union will be decided by the U.S. Supreme Court.”

“If the high court remains consistent with its acknowledgement in its [DOMA] decision of the right of states to define marriage, the states will ultimately be free to preserve man-woman marriage should they choose to do so,” he said.

The Supreme Court's 5-4 ruling on DOMA in June 2013 prohibited the federal government from denying benefits to same-sex couples who are legally married.

But social conservatives downplayed the ruling, stressing it doesn't give gays and lesbians the constitutional right to marry, and vowed to continue to fight the growing gay-rights movement.

And with so many cases pending on appeal, legal experts say it’s likely one or more will be resolved by the Supreme Court, possibly as soon as this year.

“Those cases are on fast tracks for decisions, so there is likely to be a variety of cases from which the Supreme Court could choose when it is ready to consider the constitutionality of state bans -- perhaps in the new term that opens in October,” wrote Lyle Denniston on the popular SCOTUSblog.

If the conservative-leaning high court takes another crack at the gay marriage issue, social conservatives say they expect the bench this time to rule in their favor.

But gay marriage advocates say that with legal momentum on their side, they are hoping the courts nationwide, including the Supreme Court, will continue to preserve and possibly advance the rights they have gained during the past year.

“Allowing people to marry who they love is the right thing to do, and it also strengthens our families and our communities,” said Sen. Mark R. Warner, D-Va. “Virginia should be a welcoming place for all, and I am very pleased at the rapid progress toward marriage equality that we're seeing in Virginia and around the country.”

• Wire reports were used in this article.