Amazon CEO Jeff Bezos and his wife MacKenzie have pledged to donate $2.5 million in support of Referendum 74, the Washington state ballot question which would uphold the state's gay marriage law.

The law, which was approved by lawmakers at the urging of Governor Chris Gregoire, was set to take effect last month but it was put on hold when opponents turned in more than twice the number of signatures needed to put it up to a public vote in November.

The Bezos gift more than doubles the money available to the campaign to approve Referendum 74.

In an interview with The New York Times, Zach Silk, campaign manager for Washington United for Marriage, called the donation a game changer.

“To get this from a straight, married couple sends a powerful message that marriage is seen as a fundamental question of fairness,” Silk said.

Mr. Bezos was approached via e-mail on Sunday by Jennifer Cast, a former Amazon employee who is leading fundraising for Washington United for Marriage.

The lesbian mother of four implored Bezos to get into the fight.

“Jeff, I suspect you support marriage equality. I beg you not to sit on the sidelines and hope the vote goes our way. Help us make it so,” she wrote.

On Tuesday, Bezos replied: “Jen, this is right for so many reasons. We're in for $2.5 million. Jeff & MacKenzie.”

Microsoft co-founder Bill Gates and CEO Steve Ballmer each gave $100,000 to the campaign.