LGBT people haven't done so well at winning these kind of state ballot measures; in both Maine and California, marriage victories were overturned by voters. But I wouldn't be surprised if Washington voters turn back marriage opponents in a November vote; among other strengths, they can count major state businesses like Starbucks and Microsoft in the pro-marriage equality camp. And the northwest has an honorable history of winning electoral fights over gay rights
A Washington vote to uphold a gay marriage law would repeat one of the great early successes of the LGBT rights movement. Thanks to the movie Milk, there's some historical memory of the 1978 defeat of a California initiative that would have fired out lesbian and gay teachers and silenced their supporters. But the same year, Seattle voters rejected an attempt to repeal their local ordinance that protected lesbians and gays against employment and housing discrimination. History Link tells the story.
Good friends of mine lived through the campaign adhering to "more radical" opposing positions; in fact two poured donated blood on the office of proponents and served local jail time for this act of uncivil though nonviolent disobedience.
As a political campaigner, I'm interested in lessons collected in oral histories of the victory. The Seattle Committee Against Thirteen and Women against Thirteen (SCAT/WAT) was a "more radical" group that wanted to talk about a lot more than generic privacy rights. Jan Denali explained
In the struggle for full gay rights, there simply is no doubt that repeated exposure to the humanity of ordinary gay people -- those face to face meetings that may begin in ignorance and prejudice but lead to mutual tolerance -- are what has turned the tide in our favor. We are everywhere and the end of the world (or of the family or heterosexual marriage or whatever) hasn't come. That approach worked on a citywide basis (alongside a more conventional electoral effort) as far back as 1978. It obviously works better in smaller settings and when the heat behind the issue hasn't been driven up too high by demagoguery. It probably takes a mix of campaign styles to win, but I have little doubt that victories that push back bigotry that are won with a strong component of public education are durable, in fact likely to be permanent. That 1978 campaign, super-heated and fraught as it was, laid the groundwork for marriage equality in Washington State this year.