Expanding his support for same-sex marriage onto the national stage, Mayor Michael R. Bloomberg donated $250,000 this month to support an effort in Maryland to do what no state has done so far: legalize same-sex marriage at the ballot box.
The mayor’s donation, to be announced on Friday, is the largest individual contribution received by proponents of same-sex marriage in Maryland, where voters will face a referendum in November on whether to affirm or reject a state law passed this year to allow same-sex couples to marry.
Mr. Bloomberg, a billionaire who attended college in Maryland at Johns Hopkins, dipped into his personal fortune to help persuade New York lawmakers to approve same-sex marriage in 2011, and he has supported a similar effort in New Hampshire. His contribution came after discussions with Maryland’s governor, Martin O’Malley, a Democrat who has spearheaded the effort to pass the referendum, known as Question 6.
“The fact that someone of Mayor Bloomberg’s national stature and recognition would care about our referendum campaign for civil marriage equality, I think, tells people all over our country that this is a serious and real campaign,” Mr. O’Malley said in an interview on Thursday evening from Kentucky, where he was attending the vice-presidential debate.
Mr. Bloomberg often speaks passionately about his support in the fight for same-sex marriage, which he considers a significant battle for expanding civil rights. Voters in three other states — Maine, Minnesota and Washington — will also weigh in on same-sex marriage on Election Day, offering a litmus test of popular sentiment on an issue that has never been approved by a popular vote.
“I do not believe that government has any business telling one class of couples that they cannot marry,” Mr. Bloomberg wrote in an e-mail, to be distributed on Friday morning to supporters of same-sex marriage in Maryland. “The next great barrier to full equality under the law is marriage equality. There is no doubt in my mind this barrier will fall, just as so many others have.”
With his mayoralty ending next year, Mr. Bloomberg has been developing his national profile through a series of donations to political candidates and social causes. In February, he gave a matching gift of $250,000 to Planned Parenthood after it lost funding from a breast cancer advocacy organization; his donation earned praise from progressive groups.
Governor O’Malley of Maryland said he hoped the mayor’s generosity would spur additional donations to his group, Marylanders for Marriage Equality, saying he was concerned that opponents of same-sex marriage would outspend supporters in the state. “A contribution as generous as this is certainly a big help to us,” he said.
The mayor and Mr. O’Malley have known each other for years: Mr. Bloomberg frequently travels to Baltimore, where Mr. O’Malley served as mayor, to visit his alma mater, to which he has contributed about $800 million over several decades. Mr. Bloomberg also traveled to Maryland in 2010 to endorse Mr. O’Malley’s bid for re-election.
The mayor and the governor met in New York’s City Hall over the summer to discuss the same-sex marriage referendum. Mr. O’Malley said the two had been playing phone tag since he heard about the mayor’s decision to donate last week. “We’re very grateful for the contribution,” he said.
This post has been revised to reflect the following correction:
Correction: October 12, 2012
An earlier picture caption with this article misstated the date the picture of Mayor Michael R. Bloomberg was taken. It was September, not this week.