Lawmakers are holding off on introducing legislation that would repeal the Defense of Marriage Act until after the Supreme Court rules on the anti-gay law, according to multiple sources familiar with the bill, as one Republican LGBT organization expects Sen. Rob Portman (R-Ohio) to sign on as a co-sponsor.

A number of LGBT advocates familiar with the legislation, which has been known as the Respect for Marriage Act, told the Washington Blade its lead sponsors — Rep. Jerrold Nadler (D-N.Y.) in the House and Sen. Dianne Feinstein (D-Calif.) in the Senate — are delaying introduction until after the expected court ruling in June.

Fred Sainz, HRC’s vice president of communications, said his organization supports the decision to postpone introduction of the bill until after a decision is reached in the DOMA case, known as Windsor v. United States.

“The lead sponsors of the RMA have decided to wait until after the court rules in Windsor,” Sainz said. “We support that decision and look forward to continuing to work with them to advance this important legislation.”

Ian Thompson, legislative representative for the ACLU, said his organization, which filed the lawsuit against DOMA, has a similar understanding that the lead sponsors won’t introduce the Respect for Marriage Act until the Supreme Court rules on plaintiff Edith Windsor’s challenge.

“The ACLU understands and respects that decision, and is committed to continuing to work with our sponsors in Congress and coalition partners to advance the Respect for Marriage Act and a full repeal of DOMA to ensure that the federal government recognizes and respects the marriages of same-sex couples across the nation,” Thompson said.

Still, the lawmakers are staying mum. Ilan Kayatsky, a Nadler spokesperson, said he had “no news to report yet” on the timing for the introduction of the DOMA repeal bill, and Feinstein’s office declined to comment.

In the event that the Supreme Court decides to uphold DOMA, the Respect for Marriage Act would be the next approach to lifting the 1996 anti-gay law, which prohibits federal recognition of same-sex marriage. Moreover, as previously reported by the Blade, legislation still may be necessary if DOMA is overturned to clear up lingering inequities for married same-sex couples, such as in situations where they move from one state that recognizes their union to another that doesn’t.

Previous versions of the bill had a “certainty provision” spelling out that federal benefits would continue to flow to married gay couples — even if they live in a state that doesn’t recognize same-sex marriage.

David Codell, legal director at the Williams Institute of the University of California, Los Angeles, explained that the Respect for Marriage Act “would serve important purposes” even if the Supreme Court were to strike down the ban on federal recognition of same-sex marriage.

“The Respect for Marriage Act would make clear that the federal government would treat as valid for federal purposes all marriages of same-sex couples in the United States if the marriages were valid where entered — regardless of whether a couple currently lives in a state that permits same-sex couples to marry or recognizes such marriages,” Codell said. “The Act would mean that a validly married same-sex couple could move anywhere in the country without losing federal benefits tied to marriage.”

As they await introduction of a bill, LGBT advocates say they’re continuing to work to bring on additional co-sponsors for the bill, which closed the 112th Congress with 161 co-sponsors in the House and 32 co-sponsors in the Senate. That effort was highlighted by Evan Wolfson, president of Freedom to Marry.

“Freedom to Marry’s focus right now is on continuing to add co-sponsors as we prepare to introduce the bill with the strongest momentum possible when ready to move forward,” Wolfson said.

While the House bill had Republican co-sponsors in the 112th Congress — Rep. Ileana Ros-Lehtinen (R-Fla.), Rep. Richard Hanna (D-N.Y.) and former Rep. Charlie Bass (R-N.H.) — the Senate version of the bill has never had GOP support. Even Sen. Susan Collins (R-Maine), who’s considered an LGBT advocate and champion of “Don’t Ask, Don’t Tell” repeal, wasn’t a co-sponsor.

But the Log Cabin Republicans say that will change. Gregory Angelo, the organization’s executive director, said he expects Portman — who came out in favor of marriage equality after he learned his son is gay — to be among the sponsors of the DOMA repeal.

“Congresswoman Ileana Ros-Lehtinen and Congressman Richard Hanna were Republican co-sponsors in the 112th Congress, and we have every expectation they will continue as co-sponsors when the bill is reintroduced,” Angelo said. “Given his recent evolution on marriage equality, we expect Republican Senator Portman to be a co-sponsor in the Senate.”

Angelo later clarified that he’s had no assurances from Portman that he’ll be a sponsor, but was basing his assessment on the senator’s past statements in favor of same-sex marriage.

Portman’s office didn’t respond to a request for comment on whether he’ll sign on as co-sponsor to the Respect for Marriage Act. According to a Cleveland Plain Dealer article at the time Portman came out for marriage equality, Portman told reporters he believes legally married gay couples should receive the federal benefits of marriage, but the report doesn’t quote him as saying he’ll sign on as a sponsor to DOMA repeal legislation per se.