Six days until the election and the race to watch is the Referendum 74 campaign for same-sex marriage in Washington. With polling extremely tight, the push to uphold the same-sex marriage law passed by the legislature last year has become astoundingly expensive.

Part of the reason why Basic Rights Oregon decided not to push same-sex marriage in Oregon during this election is that they estimated the campaign would cost $10 million—all of which they'd have to raise during a heated presidential election.

The six pro-marriage political action committees in Washington have actually raised a jaw-dropping $13.3 million. They've been successful at pulling in big-business donors including Bill and Melinda Gates (who donated $600,000), CEO Jeff Bezos and Mackenzie Bezos (who together gave, gulp, $2.5 million), Nike (which gave $5,000) and chief executives at Starbucks, Alaska Airlines, and Microsoft. They've also pulled in small donors from all over the country. Fifteen percent of donations for the main pro-same-sex marriage group, Washington United for Marriage, have come from out of state.

The anti-marriage side, meanwhile, has $2.27 million in its war chest. Of that, $1.49 million comes from just three sources: conservative Seattleite Thomas Matthews (who gave $100,000), the Catholic Knights of Columbus (at $306,850), and the National Organization for Marriage (at $1.08 million).

Overall, the pro-gay groups have received four times the number of donations as the anti-marriage campaign has received: Over 23,000 donations compared to just 5,025. If Referendum 74 does pass, Washington is in for a payday of an expensive same-sex wedding spree.

But even with a six-to-one fundraising advantage, the race might come down to a few hundred votes. “You’re fighting for social change—that doesn’t come easy,” says Referendum 74 spokesman Zach Silk. “If we win, we’ll be glad we went. If we lose narrowly, we’ll have moved the needle significantly.”