PORTLAND, Maine — The Maine Education Association voted Sunday to endorse the referendum on the November ballot that would allow same-sex couples in Maine to marry.

“We are grateful for the support of the Maine Education Association and for the organization’s vote to endorse the campaign to allow same-sex couples to receive a marriage license,” Matt McTighe, campaign manager for Mainers United for Marriage, said Thursday in a press release. “The MEA is one of the largest and most well-respected organizations in the state, with members in every community. We are proud to welcome them to our coalition.”

Carroll Conley, head of the Christian Civic League of Maine and the Protect Marriage Maine political action committee, said Thursday that he was disappointed but not surprised by the announcement. Conley and the Rev. Bob Emrich of Plymouth head up the PAC opposing the referendum.

“We certainly aren’t surprised by the actions of the leadership of the Maine Education Association when we consider their stands on other issues,” Conley said. “My question is: How this is germane to their educational mission? I’d like to see if they polled their membership because you’ll never convince me this represents the rank and file teachers in the MEA.”

The voice vote to endorse the referendum happened Sunday during the organization’s annual convention of elected leaders from around the state, Rob Walker, executive director of the MEA, said Thursday in a telephone interview.

“Our representative assembly is made up of leaders from local associations,” he said. “It is a yearly event where a budget is passed and officers are elected among other things.”

Walker estimated there were about 120 delegates in attendance when the vote was taken. The motion passed without objection, he said.

MEA opposed the repeal of the same-sex marriage law in 2009, Walker said. Over the last 25 years, the organization has supported efforts to include sexual orientation in the Maine Human Rights Act, extending benefits to domestic partners and same-sex marriage.

Mainers on Nov. 3, 2009, voted 53 percent to 47 percent to repeal a law that allowed same-sex couples to marry. It had been passed by the Democrat-controlled Legislature and signed into law by Gov. John Baldacci in the spring of 2009. After the loss at the ballot box, EqualityMaine, a member organization that works on issues of importance to gay, lesbian, bisexual and transgender individuals, began an outreach campaign to talk about the issue and began gathering signatures in August 2011 to put a question before voters again.

An Associated Press analysis of the 2009 election attributed opponents’ victory to the use of ads that said if the same-sex marriage law was allowed to stay on the books, children would be taught homosexuality in schools. A nearly identical ad campaign was successful in repealing a gay marriage law in California, according to The Associated Press.

“Article 2 of our constitution supports civil rights for all,” Walker said of MEA’s support for same-sex marriage and other gay rights issues. “That is the guide for us.”

The 150-year-old organization represents more than 24,000 active and retired teachers.