Opponents of Referendum 74 conceded defeat on Thursday, a day after supporters declared victory.

Washington state now joins Maine and Maryland as the first states to approve gay marriage at the ballot box.

“We are disappointed in losing a tough election battle on marriage by a narrow margin,” said Joseph Backholm, campaign chairman of Preserve Marriage Washington, the primary group opposing the measure.

“The election results reflect the political and funding advantages our opponents enjoyed in this very liberal and secular state,” he said in a statement. “The results show only that in a deep blue state, with a huge financial advantage, gay marriage activists can win – barely.”

Late Thursday, the AP called a win for Referendum 74. With 73% of precincts reporting, the measure was up by nearly 5 points, 52.3% to 47.7%.

The measure is similar to Maryland's Question 6, both of which uphold marriage laws approved by lawmakers.

Gay couples in Washington can begin applying for marriage licenses on December 6. After a 3-day waiting period, the first weddings are expected to take place on Sunday, December 9. Maryland's law takes effect on January 1.