Gov. Christine Gregoire

The Washington state senate is expected to pass a marriage equality bill Wednesday — legislation that Gov. Chris Gregoire has promised to sign into law.

The senate will likely vote on the bill late Wednesday afternoon or early evening. Though the vote margin in the senate chamber is extremely narrow, the bill is expected to pass in the house by a wide margin.

If passed, Washington would become the seventh state plus the District of Columbia to extend equal marriage rights for same-sex couples. But marriage equality opponents including the National Organization for Marriage have vowed to take the issue to a voter referendum and to fund primary challenges to Republican lawmakers who voted in favor of gay marriage.

On Tuesday, Washington state senator Ed Murray, an openly gay lawmaker and lead sponsor of the bill, told The Advocate he remains confident that the 25 pledged votes needed to pass the legislation remain solid.

Murray said he expects Gov. Gregoire to sign the bill late next week, though he anticipates a referendum on the issue later this year