Jeff Bezos, the billionaire founder of Amazon.com and his wife, MacKenzie, have agreed to donate $2.5 million to help pass a same-sex marriage referendum in Washington State, instantly becoming among the largest financial backers of gay marriage rights in the country.

The 2.5 million dollar gift, doubles the money available to the proponents of Referendum 74, which will legalize same-sex marriage in the state by affirming a law that passed the Legislature this year.

Same-sex marriage was legalized by Washington’s States Legislature last February after a push by Gov. Christine Gregoire,. But opponents collected enough signatures to put the legislation to the voters.

Jennifer Cast, one of Amazon’s earliest employees, who was able to buy Amazon shares UK and a lesbian mother of four children who is now a fund-raising chairwoman of the pro-referendum effort sent Mr. Bezos and his wife an e-mail asking for help.

In her e-mail, sent Sunday evening, Ms. Cast, 50, implored Mr. Bezos to understand the importance of the issue to her and her longtime partner.

“I want to have the right to marry the love of my life and to let my children and grandchildren know their family is honored like a ‘real’ family,” Ms. Cast wrote. “We need help from straight people. To be very frank, we need help from wealthy straight people who care about us and who want to help us win.”

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

And Jeff and MacKenzie Bezos has.

Well done and Thank you.