OLYMPIA — A measure to legalize same-sex marriage in Washington state was introduced Friday in the Senate, where the measure was just two votes shy of having enough support to pass.

The bill, requested by Gov. Chris Gregoire, is sponsored by Sen. Ed Murray, D-Seattle, a gay lawmaker who has led the fight for gay civil rights and domestic partnerships. While the House is widely expected to have enough support, the Senate is still short of the 25 votes needed for passage there.

Even though 22 other senators signed onto the bill in support, including two Republicans, Murray played down expectations.

“I am two votes short,” he said. “This is as likely not to happen as to happen. At this point, it’s a very personal decision for the members.”

Sen. Rosemary McAuliffe, D-Bothell, committed her vote Friday to approve the measure after initially saying she was leaning in favor of support but unwilling to commit to it.

McAuliffe, who is one of the co-signers on the bill, said that the legislation is long overdue.

In a tally by The Associated Press, three Democratic members who have previously cast votes against expanding options for gay couples — Sens. Brian Hatfield of Raymond, Jim Kastama of Puyallup and Paull Shin of Edmonds — have said they’re weighing the issue but haven’t decided how to vote.

Hatfield said Friday he is willing to support a vote of the people on gay marriage but is still torn on how he would approach a vote in the Legislature.

Sen. Mary Margaret Haugen, D-Camano Island, issued a statement Thursday saying she was listening to all sides and keeping an open mind.

“I feel the best option is to send it to the voters on a referendum, but I’m still hearing from constituents and I want them to have full opportunity to make their views known,” she said in a written statement.

Murray has insisted that he will not support adding a referendum clause to the bill, saying minority rights should not be decided at the ballot.

The two Republican senators who support gay marriage are Steve Litzow of Mercer Island and Cheryl Pflug of Maple Valley. Two first-term Republicans representing suburban districts — Sens. Joe Fain of Auburn and Andy Hill of Redmond — left open the possibility of supporting the bill, saying they want to discuss the issue with constituents. They have declined to say whether they were leaning in any direction.

The first public hearing on the bill is expected on Jan. 23.

Joseph Backholm, executive director of The Family Policy Institute of Washington, said he expects thousands of people to show up at the public hearing in opposition.

“The idea that there is no difference between a heterosexual relationship and a homosexual relationship and that the law should recognize no difference, assumes there is no difference between men and women,” he said. “This would be the state taking a position and saying ‘We will no longer encourage arrangements that will give children both a mother and father.’”

Washington state has had a domestic partnership law since 2007. The measure that benefited from momentum from a gay civil rights law that passed the previous year.

A so-called “everything but marriage” bill was passed in 2009, greatly expanding that law. Opponents later challenged it at the ballot box, but voters upheld the law. Nearly 19,000 people in Washington are registered as domestic partners.

One opponent already has filed an initiative seeking to clarify the definition of marriage.

On Monday, Everett attorney Stephen Pidgeon filed a proposed ballot initiative that seeks to change the current state statute, which says marriage is a civil contract between a male and a female. Pidgeon previously worked with groups that unsuccessfully tried to overturn the state’s domestic partnership law. He wants marriage to be defined being “between one man and one woman.”

Backholm declined to comment on whether his group was supportive of or working with Pidgeon on the initiative.

To qualify for the November ballot, sponsors of the latest initiative must submit at least 241,153 valid signatures of registered voters by July 6.

Same-sex marriage is legal in New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont and the District of Columbia.