She has joked about caterer tastings and trying on dresses. She has sent out hundreds of invitations, sprinkled with references to an early romantic getaway at the Pierre hotel and a shared affection for the Jersey Shore. In just a few weeks, she will walk down the aisle, with brooches from her mother fastened in her hair and surrounded by wildflowers meant to evoke those on the High Line.


After years of advocating for the right of gay men and lesbians to marry, Christine C. Quinn, the speaker of the New York City Council, is about to become one of the most prominent elected officials in the nation to marry someone of the same sex.


On the evening of May 19, Ms. Quinn will marry her girlfriend, Kim M. Catullo, at the Highline Stages, an event space in the meatpacking district. Judith S. Kaye, a former chief judge of the state, will officiate; the nearly 300-person guest list includes the mayor, the governor and New York’s two United States senators.


The wedding is a personal event for Ms. Quinn, but it is also freighted with political significance, coming just a year before Ms. Quinn is expected to ask New Yorkers to elect her as their mayor.


“There’s really not a political implication to this for me as it relates to electoral politics,” Ms. Quinn said in an interview. “We’re trying to make it really a day, a night that’s about friends and family and us.”


But Ms. Quinn’s personal story is attracting increasing attention beyond the City Hall press corps that ordinarily covers her — in recent months she has been the subject of profiles in The New Yorker and Elle, for which she was photographed on the Brooklyn Bridge wearing designer clothes and in which she talked about her recent weight loss and her engagement ring.


Ms. Quinn and her team are taking a cautious approach in responding to news media interest in the wedding. While Ms. Quinn has talked during public appearances about how much fun she is having planning the event, she and her aides have closely guarded the details about the event, saying that it is a private moment. They did release a copy of the save-the-date notice, and said that although members of the news media would not be allowed in the wedding, they expected to release a photograph or two. Ms. Quinn agreed to speak generally about the wedding; Ms. Catullo, a products liability lawyer, declined to be interviewed.


Longtime observers of the New York political scene said the wedding could benefit Ms. Quinn, as it would give her an early chance to share her story with voters and to underline the historic nature of her candidacy — if elected she would be the first woman and the first openly gay person to lead the nation’s largest city. The wedding will also offer Ms. Quinn, sometimes portrayed as a brash and sharp-tongued leader, a chance to soften her image.


“She comes over, typically, as a rather tough politician,” said Kenneth Sherill, a professor of political science at Hunter College. He said the wedding could be a humanizing moment for Ms. Quinn.


“It puts a warm and loving face on a politician, at a time when we don’t think of politicians that way,” he said.


But Ms. Quinn also has to be cautious about not appearing to use a personal moment for political gain, analysts said.


“It’s a very tough balance that you have to achieve,” said Matthew Hiltzik, a public relations strategist who has advised Democratic politicians and other public figures, including Alec Baldwin and Katie Couric.


“If you provide too much information, then someone will accuse you of exploiting it,” he said. However, he said, his sense was that Ms. Quinn and Ms. Catullo are, so far, striking the right balance.


Other likely candidates for mayor are increasingly calling attention to their own personal stories. All of the other expected candidates are married men with children, and two of those candidates’ wives, Elyse Buxbaum, the wife of the Manhattan borough president, Scott M. Stringer, and Chirlane McCray, the wife of the public advocate, Bill de Blasio, have recently taken to Twitter, where they have posted pictures of, and news about, their children. (Mr. Stringer and Ms. Buxbaum married in Connecticut in 2010 to protest that at the time same-sex couples could not marry in New York.)


Even in New York City, Ms. Quinn’s same-sex wedding carries some political risk, because pockets of the city are socially conservative.


“We don’t know what the reaction will be, because we’ve never had something like this,” said Hank Sheinkopf, a Democratic political consultant.


But Michael A. Krasner, a professor of political science at Queens College, said that many of the voters who might take issue with a same-sex wedding would probably not vote in a Democratic primary. (At the moment, all the expected candidates for mayor are Democrats.)


“My hunch is that, while there may be some impact at the margins in terms of a Democratic primary,” he said, “it’s not going to matter very much, because the people who vote in Democratic primaries are not people who are going to be offended by this.”


The officials invited to the wedding include the Senators Charles E. Schumer and Kirsten E. Gillibrand, and two county Democratic leaders, Vito J. Lopez, an assemblyman from Brooklyn, and Joseph Crowley, a congressman from Queens.


Ms. Kaye, the former judge who will perform the wedding, played a small role in the history of same-sex marriage in New York, authoring an impassioned dissent in 2006 to a court ruling rejecting the right of gay couples to marry. In her dissent, Ms. Kaye said that future generations would look back on that as “a serious misstep.”


Ms. Kaye also officiated at the same-sex wedding in January of Assemblyman Daniel J. O’Donnell, a Manhattan Democrat, before a crowd of more than 400 guests.


Ms. Quinn and Ms. Catullo, both 45, met in 2001, when they were set up by mutual friends. They immediately hit it off, and learned that they shared some personal background, as well. Both had lost their mothers as teenagers, and both remained close to their fathers, Roman Catholics who over the years had come to accept their daughters’ sexual orientation.


During the fight to legalize same-sex marriage in New York, Ms. Quinn repeatedly invoked her relationship with Ms. Catullo as an example of what was at stake in the legislative battle: The couple wanted to be able to get married, Ms. Quinn often said, while their fathers were still alive and could attend the wedding.


After the bill legalizing same-sex marriage passed the Legislature last year, Ms. Quinn wiped away tears as she said how excited she would be to go to a family gathering the next day and, for the first time, discuss her own wedding plans, including what dress Ms. Catullo’s grandniece might wear as a flower girl.


“I really can’t really describe what this feels like,” Ms. Quinn said at the time, “but it is one of the best feelings I have ever had in my life.”