SEATTLE — Washington was poised Wednesday to become the seventh state to allow same-sex couples to marry after the State House gave final passage to such a bill. Gov. Christine Gregoire promised to sign it.

The governor is expected to do just that as soon as next week, but it is not likely to take immediate effect. Under state law, if opponents gather 120,000 signatures, the measure will be put to a public referendum before it can be enacted.

The Washington vote came just a day after a court ruling in California that struck down that state’s ban on same-sex marriage, and it precedes several other votes expected across the country that could keep the issue in the spotlight throughout this election year. Some will take place in legislative chambers, including in Maryland and New Hampshire, and some at the ballot box, including in Minnesota, North Carolina and, very likely, a referendum here in Washington on the bill the Legislature just passed by a vote of 55 to 43.

Advocates on both sides said Wednesday that, over the long term, their side would prevail, regardless of the conflicting developments that have defined the issue for several years.