And this time around, it looks like Washington could very well become the 7th state plus the District of Columbia to legalize same-sex marriage.
Gay marriage has won the backing of several prominent Pacific Northwest businesses, including Microsoft Corp. and NIKE, Inc., and just this week a conservative Democrat who once opposed same-sex marriage said he will now vote for it.
Bills to legalize same-sex marriage have been introduced in the House and Senate, sponsored by two gay lawmakers who have pushed for gay rights measures in past years. The bills will have their first public hearings on Monday, before a Senate committee in the morning and a House committee in the afternoon. While gay marriage bills have been introduced in Washington state before, this is the first time the issue will receive a public hearing.
"If there's one word to sum up where Washington is on marriage equality, it's momentum," said Michael Cole-Schwartz, a spokesman for the Washington, D.C.-based Human Rights Campaign.
Same-sex marriage is legal in New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont and the District of Columbia. Lawmakers in New Jersey and Maryland are expected to debate gay marriage this year as well.
Washington state along with several other states, including California, Oregon and New Jersey, have laws that either recognize civil unions or domestic partnerships that afford same-sex couples some or nearly all of the rights to marriage.
The debate over same-sex marriage in Washington state has changed significantly since lawmakers passed Washington's Defense of Marriage Act in 1998. The constitutionality of DOMA was ultimately upheld by the state Supreme Court in 2006, but earlier that year, a gay civil rights measure passed after nearly 30 years of failure, signaling a change of mindset in the Legislature.
The quick progression of domestic partnership laws in the state came soon after, with a domestic partnership law in 2007, and two years of expansion that culminated in 2009 with the so-called "everything but marriage law" that was upheld by voters after opponents filed a referendum to challenge it.
That slow-but-steady strategy was spearheaded by Democratic Sen. Ed Murray, a gay lawmaker from Seattle who has led the push for gay civil rights and domestic partnerships and who is sponsoring the Senate marriage bill.
Murray said that it may have taken years to lay the groundwork, but now the state is ready to address same-sex marriage.
"The culture changes and the politics follows," he said. "The most political act that changed the culture wasn't in Olympia, it wasn't me. It was people coming out to their families, to their workplace. That's what's changed people's minds."
Momentum continued to build last week, when Microsoft and several other companies, including RealNetworks Inc., NIKE Inc. and Vulcan Inc., sent Gov. Chris Gregoire a letter Thursday saying they supported the two measures. Also on Thursday, Sen. Jim Kastama of Puyallup announced he would support the measure in the Senate, becoming the 24th senator to commit a vote to the measure. The state House is widely expected to have enough support to pass gay marriage, and Gregoire publicly endorsed the proposal earlier this month.
The state Senate is now just one vote shy of having enough backing to approve the bill, with a half-dozen lawmakers remaining uncommitted.
In October, a University of Washington poll found that an increasing number of people support same-sex marriage. About 43 percent of respondents said they support gay marriage, up from 30 percent in the same poll five years earlier. Another 22 percent said they support giving identical rights to gay couples but just not calling it marriage.
When asked how they would vote if a referendum challenging a gay marriage law was on the ballot, 55 percent said they would vote yes to uphold the law, with 47 percent of them characterized as "strongly" yes, and 38 percent responded "no," that they would vote to reject a gay marriage law.
If a marriage bill were passed, gay and lesbian couples would be able to get married starting in June unless opponents file a referendum to challenge it at the ballot.
Under the bills being considered by the Legislature, people currently registered in domestic partnerships would have two years to either dissolve their relationship or get married. Domestic partnerships that aren't ended prior to June 30, 2014, would automatically become marriages.
Domestic partnerships would remain for senior couples where at least one partner is 62 years old or older. That provision was included by lawmakers in 2007 to help seniors who don't remarry out of fear they could lose certain pension or Social Security benefits.
The measure doesn't require religious organizations or churches to perform marriages, and doesn't subject them to penalties if they don't marry gay or lesbian couples.
But several religious groups have opposed any discussion of gay marriage. This month, the Catholic bishops of Washington issued a statement saying that same-sex marriage was not in the public interest and calling on "the citizens of this state to maintain the legal definition of marriage."
Joseph Backholm, executive director of The Family Policy Institute of Washington, said that the debate "really does go to the core of who we are, and what matters in the big picture."
"What we're being offered is that marriage is for the purpose of validating relationships. If that is true, that is a shaky foundation and one that establishes precedent that no one wants to follow," he said.
Earlier this week, the National Organization for Marriage announced that it would spend $250,000 to help fund primary challenges to any Republican who crosses party lines to vote for same-sex marriage in Washington state. So far, two Republicans in the Senate, and two in the House have said they would vote in support of gay marriage.
Rep. Jamie Pedersen, a Democrat from Seattle who is sponsor of the House bill, said that even if a gay marriage law doesn't pass this year, the stage has been set for future success.
"This change is inevitable," he said. "It's just a question of how long the families of same-sex families are going to have to wait for that justice to be done."
The gay marriage bills are Senate Bill 6239 and House Bill 2516.