The group working to keep Washington state's gay marriage law said Monday they raised more than $952,000 in June.

“Our supporters made 4,744 contributions and raised $952,267 for the campaign to defend marriage equality in Washington and approve Referendum 74,” Zach Silk, campaign manager for Washington United for Marriage, said in an e-mail to supporters. “And 79% of our contributions were less than $100.”

“Another very cool stat: 90% of the donations in June came from Washingtonians,” Silk added.

In a video message released Monday, Silk thanked supporters: “Thanks to your early investment, we know that we can win this campaign.” (The video is embedded in the right panel of this page. Visit our video library for more videos.)

Tuesday is the deadline for initiative campaigns to file their monthly campaign finance reports with the state Public Disclosure Commission.

Included in the June total were two $100,000 donations from Microsoft CEO Steve Ballmer and co-founder Bill Gates.

Supporters said they have raised more than $2 million for the campaign.

Referendum 74 will ask voters in November to uphold – or reject – a law legalizing gay marriage approved by lawmakers.

Silk said he expects fundraising efforts by opponents to spike in the fall.

“We can't take anything for granted,” he said.

Preserve Marriage Washington, the group which put Referendum 74 on the ballot, has raised more than $135,000 as of the end of May, according to public records. The group is expected to release June totals on Tuesday.

(Related: Narrow majority of Washington voters support gay marriage.)