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WASHINGTON -- Voters in Maryland and Maine on Tuesday approved measures to allow same-sex marriage, marking the first time gay marriage has been approved by statewide popular votes.
In all, voters in four states -- Maine, Maryland, Minnesota and Washington -- considered the ballot measures.
In Washington and Minnesota, the votes were too close to call early Wednesday.
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Proponents of same-sex marriage were happy to celebrate their first victories by popular vote.
"Tonight we've taken the talking point away that marriage equality cannot win at the ballot box," said Fred Sainz, vice president of communications with the Human Rights Campaign, which invested millions of dollars in same-sex marriage initiatives.
Sainz gave some of the credit for the victory to President Obama's support for same-sex marriage.
The president said that his decision was informed by speaking with Americans, including servicemen and women he met during the work to end Don't Ask Don't Tell.
Obama's challenger Mitt Romney had said that he would support and champion legislation defining marriage as between a man and a woman.
But in general, Sainz said he thought Americans have become more understanding of why gay and lesbian couples want to marry.
"The hearts and minds of the American public have changed," he said. "For years now, we've been having a long extended conversation and connecting with them about how marriage equality is about love, family and commitment, which are common human factors."
Opponents of same-sex marriage dismissed that argument, however. Brian Brown, president of the National Organization for Marriage, noted that dozens of states have passed laws defining marriage as between a man and a woman.
He called states like Maryland "the most liberal of liberal states" and not a proxy for the general population.
"For the gay marriage groups to win in the most liberal states is not a tipping point at all," Brown said.
The measures come as American appear to be growing more comfortable with the idea of gay marriage.
A Pew Research Center poll this summer found that 48 percent of Americans favor same-sex marriage, up from 31 percent in 2004.
Democrats were the strongest proponents, with 65 percent favoring same-sex marriage in the Pew survey. Only 24 percent of Republicans favor gay marriage, while 51 percent of independents favor it.
There are some states that issue marriage licenses to same-sex couples following legislative or court action. Those include Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and the District of Columbia, according to the National Council of State Legislatures.
More than 30 states, including Arizona, Colorado and Texas, have laws or constitutional provisions defining marriage as between a man and a woman, according to the National Council of State Legislatures.
Colorado and Washington, meanwhile, voted to approve state initiatives legalizing marijuana, while Oregon voters turned away a similar initiative, projections show.
"The voters have spoken and we have to respect their will. This will be a complicated process, but we intend to follow through," Colorado Gov. John Hickenlooper said in a statement released late Tuesday.
"That said, federal law still says marijuana is an illegal drug, so don't break out the Cheetos or Goldfish too quickly."