Washington Sen. Mary Margaret Haugen announced her support for same-sex marriage on Monday.

Story highlights

"This issue isn't about just what I believe," a key state senator says

Her support means same-sex marriage will likely pass the state legislature

Opponents say they will try to put a referendum on the ballot to overturn it

CNN  — 

Washington moved closer to being the seventh U.S. state to allow same-sex marriage Monday when a key state senator announced her support.

Mary Margaret Haugen said she would be the 25th vote in the 49-member Senate for the bill. Supporters say the legislation already has a majority behind it in the state House of Representatives, and Gov. Christine Gregoire has said she would sign it if passed.

“For me personally, I have always believed in traditional marriage between a man and a woman,” Haugen, a Democrat from the Puget Sound community of Camano Island, said in a statement on her decision. “That is what I believe, to this day.

“But this issue isn’t about just what I believe,” she continued. “It’s about respecting others, including people who may believe differently than I. It’s about whether everyone has the same opportunities for love and companionship and family and security that I have enjoyed.”

News of Haugen’s statement won a standing ovation from supporters in a crowded legislative office building in Olympia, where a Senate committee held a hearing on the bill Monday afternoon. Rep. Laurie Jinkins, D-Tacoma, said Haugens was “at the end of a long line of folks” who have stepped forward to support the bill – “and we’ll likely have more that will come.”

Gregoire is “150% supportive of this legislation,” her legislative director, Jim Justin, said Monday. The two-term Democrat has touted the support of major employers like Microsoft, Nike and RealNetworks, which she called “courageous and appreciated.”

But opponents told the Senate Government Operations Committee that they weren’t done fighting. Joseph Backholm, director of the Family Policy Institute of Washington, said the issue should be put to a statewide vote.

“If we as a state are going to take the position that mothers and fathers are interchangeable and replaceable, if we are going to send a message to fathers and potential fathers in this state that it isn’t important to be in the lives of their children because dads specifically don’t matter, that is something we should all do together,” he said.

Backholm said same-sex marriage has lost in all 31 states where the issue has been decided by referendum, and that opponents would start collecting signatures to repeal it by popular vote if it passes.

“I am confident that this state, like every other state that has had the option, will weigh the evidence and ultimately conclude that moms and dads do matter,” he said.