By Jonathan Kaminsky
OLYMPIA, Washington (Reuters) - Gay marriage opponents conceded defeat on Thursday in their bid to block passage of a referendum legalizing same-sex matrimony in Washington state, two days after Maine and Maryland became the first states to approve similar measures at the ballot box.
Although votes were still trickling in from Washington's mail-in-only election, approval of same-sex marriage was firmly in the lead, 52 percent to 48 percent, prompting both sides to agree that passage was assured.
A spokesman for the Washington secretary of state's office said about two-thirds of the projected 3.1 million ballots cast had already been counted as of Thursday afternoon.
"We are disappointed in losing a tough election battle on marriage by a narrow margin. But while we are disappointed, we are not defeated," Joseph Backholm, chairman of Preserve Marriage Washington, said in a statement conceding defeat.
But he said the outcome, in a liberal Western state, did not "represent a sea change" in the view that "children need both a mother and a father."
"We are fighting for a cause that is true, and beautiful, and right — the sacred institution of marriage," he said.
Gay marriage proponents behind Referendum 74 declared victory on Election Night.
The votes in the three states have been hailed as a watershed moment by gay-rights activists. While same-sex unions had already been legalized in six states and the District of Columbia by lawmakers or courts, gay marriage had never been enacted by popular vote before Tuesday.
Meanwhile, voters in more than 30 states have approved constitutional bans on gay marriage.
The Democratic-controlled Washington state legislature voted earlier this year to legalize same-sex marriage, and Governor Chris Gregoire, a Democrat and a Catholic, signed the measure into law in February.
But the law was blocked pending Tuesday's vote after opponents submitted a petition for repeal, placing the question on the November ballot.
"Washington has made history, and I couldn't be prouder. Voters stood up for what is right and what is just and said that all Washington families are equal under the law," Gregoire said in a statement. "I am proud that our LGBT families will no longer be treated as separate but equal. They will be equal."
"This is a day that historians will look back on as a turning point for equality," she said.
(Reporting by Jonathan Kaminsky; Editing By Cynthia Johnston and Steve Gorman)