Microsoft Corp. CEO Steve Ballmer and co-founder Bill Gates are each donating $100,000 to the campaign supporting the state's new gay marriage law, which faces a referendum vote in November.
Zach Silk, campaign manager for Washington United for Marriage, says the checks were cut on Friday and were reported to the state Public Disclosure Commission Monday afternoon.
Referendum 74 was certified for the ballot last month after gay marriage opponents turned in more than 240,000 signatures last week, far more than the minimum of 120,577 valid voter signatures required.
The referendum seeks to overturn the law passed earlier this year allowing same-sex marriage in the state. That law was passed by the Legislature and signed by Gov. Chris Gregoire in February.
The law was supposed to take effect June 7 but was put on hold once the signatures were turned in.