By Michael Barbaro

Scott M. Stringer, the Manhattan borough president, buys his bagels at H&H, his groceries at Fairway and his coffee at Lenny’s (Starbucks is, after all, a Seattle company). He roots for the Jets, exercises in Riverside Park and pops into the Museum of Natural History.

Hiroko Masuike for The New York Times

The idea of doing anything outside New York City seems alien to him.

“I can’t imagine not being in this city,” he said over coffee.

But after five decades of municipal fidelity, Mr. Stringer is refusing to do something rather momentous in the city of his birth: marry.

He and his fiancée, Elyse Buxbaum, have decided to wed in Connecticut this year in what they described as a protest of New York’s failure to legalize gay marriage.

In the half year since the New York State Senate defeated a bill to allow same-sex marriage, a parade of politicians have proclaimed their anger at the inability of gay couples to marry in the state.

But Mr. Stringer, a potential candidate for mayor in 2013, may be the first to boycott New York’s marriage bureau — an act that he hopes will encourage his constituents (and fellow lawmakers) to get married in states like Connecticut, Vermont and Massachusetts that have sanctioned gay marriage.

“This gives Elyse and I a chance to take personal responsibility,” Mr. Stringer, 50, said at a coffee shop on the Upper East Side as Ms. Buxbaum, 38, sat next to him.

“If enough people who have somewhat of a profile — not just politicians, but artists and business leaders — start going into Massachusetts or Connecticut and show New York how embarrassing it is that you can’t get a marriage license for same-sex couples, then we will change things.”

The couple said they did not set out to make a statement.

They met about five years ago, shortly after Mr. Stringer’s 2005 election as borough president, when she visited his office to introduce herself and the Jewish Museum, where she is director of corporate and government relations.

They dated, on and off, in the past two years (“We never lasted in the summer,” Ms. Buxbaum said playfully). At the beginning of 2010, their relationship became serious, and Mr. Stringer proposed.

“I love a campaign,” Mr. Stringer said of his courtship.

“And, as always, he won,” Ms. Buxbaum retorted.

They briefly considered dashing down to the city clerk’s office for a quick, no-fuss wedding, the first wedding for each of them. Fearing parental reactions, however, they abandoned the idea, in favor of a traditional Jewish ceremony. But then Ms. Buxbaum started to tell her gay friends and colleagues about her impending nuptials.

“I started to feel terrible,” she said. “I was sharing something that not everybody could have.”

Breaking the news to a longtime friend who is a lesbian proved especially painful.

“She and I both went to the same college, the same graduate school, we both work in museums, and are both in long-term, loving relationships,” Ms. Buxbaum said, “and I could not figure out why my love for Scott was more worthy than her love for her partner. It just wasn’t right.”

She sat Mr. Stringer down and told him about her frustration, which he shared. “What do we do about it?” she said.

Mr. Stringer relayed their unhappiness to his longtime friend Allen Roskoff, a gay activist, who told him the solution was obvious: leave New York.

“You can do something about it,” Mr. Roskoff recalled telling Mr. Stringer. “Make a statement. Get a marriage license in a state that has marriage equality.”

Ms. Buxbaum said, “It was brilliant.” Her only concern was whether Mr. Stringer, as Manhattan’s borough president — and, more or less, a paid cheerleader for the city — could really leave New York for his wedding. “Would it look …,” Ms. Buxbaum said, trailing off.

Mr. Stringer jumped in. “We both agreed it was the right thing to do.”

“To the degree that you have a public platform, this is a very good way to use it,” he said.

Ms. Buxbaum researched their options. They settled on obtaining a marriage license in Connecticut, where they will hold a civil ceremony, with both sets of parents present. Back in New York, a rabbi will perform a religious service for about 200 family members and friends a few days later, on Sept. 5.

No agency appears to keep statistics on how many heterosexual couples shun New York to protest the lack of same-sex marriages here. While Mr. Stringer said he was not doing so for political gain, it could raise his standing among gay and lesbian voters, a significant constituency in the city.

Mr. Roskoff called the out-of-state wedding “a major statement that advances the cause.”

“It shows conviction,” he said.

Mr. Stringer is not new to the marriage debate. As a member of the State Assembly, he helped introduce the state’s first bill to legalize same-sex marriage in the 1990s. But even as he acknowledged the political symbolism of his wedding, he said it was really a question of conscience.

“I don’t view this as a politically courageous act,” Mr. Stringer said. “This is something we are going to do personally that we will have with us for the rest of our lives.”