The state senate, over opposition from Republicans opposed to gay marriage, seems certain to pass a marriage-equality bill tonight. (Members of the state house overwhelmingly support the bill.)

Assuming tonight's vote (the bill is sponsored in the Senate by Ed Murray, D-43) goes as expected, what happens next?

According to legislative staffers, once the bill passes in the senate, it will move on to the house, where Murray hopes to see a vote within the next few days. Worst-case scenario: It could take a week or so. After that, Gov. Chris Gregoire will sign it (as she has pledged to do), and gay-rights opponents will respond by filing a referendum to overturn the legislation.

Assuming that happens, the law will effectively go into suspended animation. The law allowing gay marriages would go into effect on June 7, and the deadline for opponents to submit signatures on a referendum is June 6. If they submit what appears to be enough signatures (a minimum of 120,577 valid signatures are required to certify a referendum), according to Washington Secretary of State Sam Reed's spokesman Dave Ammons, the new law would be in a state of "abeyance" until voters have their say on the referendum in November and the election is certified.

The upshot: If voters uphold same-sex marriage, gay couples could start getting married in Washington on December 7, 2012, Ammons says.