BOSTON -- Boston Mayor Thomas Menino, struggling to keep his emotions in check, told well-wishers gathered at historic Faneuil Hall on Thursday that he won't seek re-election to an unprecedented sixth term after nearly two decades in office.

"I am here with the people I love, to tell the city I love, that I will leave the job that I love," Menino said, with his wife Angela and family by his side. "I can run, I can win and I can lead, but not in the neighborhoods all the time as I like."

Menino, who used a cane to walk to the podium, has had persistent health problems including a six-week hospital stay last year to treat a respiratory infection and a compression fracture in his spine. Menino also was diagnosed with Type 2 diabetes.

But the city's longest serving mayor told the crowd that he is on the mend. Still, he said, it's not enough to maintain the pace that has become his trademark.

"I'm back to a mayor's schedule, but not a Menino schedule," he said. "Spending so much time in the neighborhoods gives me energy.... It may not be the only way to lead Boston, but it's the only way for me."

Menino spoke for about 12 minutes and received a three-minute standing ovation.

During his comments, Menino alluded to a poll that once indicated that more than half of the city's residents had said they'd personally met him.

He also acknowledged that his decision not to run again is expected to trigger a political stampede.

"I have no plans to pick the person to fill this seat," he said. "I just ask that you choose someone who loves this city as much as I do."

President Barack Obama praised Menino.

"Boston is the vibrant, welcoming, and world-class city it is today because of Tom Menino," Obama said in a statement. "For more than two decades, Mayor Menino has served the city and every one of its residents with extraordinary leadership, vision, and compassion."

Democratic U.S. Sen. Elizabeth Warren, who won a critical endorsement from Menino in last year's U.S. Senate race called him "the best mayor in America" and "the best friend to the neighborhoods and people of Boston."

Although Menino wasn't always the smoothest of political figures, he earned a reputation as one of the hardest working, from filling potholes to shaping the city's skyline.

A recent Boston Globe poll showed the 70-year-old Menino was viewed favorably by a wide margin of city residents, although less than half said they wanted him to run again. Most political watchers assumed Menino could have cruised to another victory.

Menino said he's not done yet.

"I have nine months left. Just think what I can do in nine months," he said. "We can have some real fun."

Menino's long stewardship of the city came a critical moment in Boston's history when traditional urban ethnic enclaves began to give way to waves of new immigrants and younger professionals.

He worked to make Boston more fun and livable. Despite its famously narrow, twisting streets, Menino ushered in a bicycle-sharing program and named a "bicycle czar" to negotiate conflicts between bicyclists and Boston drivers.

He also struggled to try to improve the Boston school system and wasn't shy about wearing his sympathies on his sleeve.

Last year Menino, a strong gay rights supporter, vowed to block Chick-fil-A from opening a restaurant in the city after the company's president spoke out publicly against gay marriage.

Lawrence DiCara, a former city councilor, said Menino's success stemmed from his attention to detail and – unlike many of his predecessors – his lack of interest in higher office.

"He kept his eye on the ball," DiCara said. "He was not interested in running for governor. He was not interested in running for Congress. He had one thing he wanted to do and that was being mayor of Boston."

Menino was the city's first Italian-American mayor, breaking a nearly century-long domination of city politics by Irish-Americans that began with John "Honey Fitz" Fitzgerald, the grandfather of President John F. Kennedy and Sens. Robert and Edward Kennedy, and included the legendary James Michael Curley.

Menino grew up in Hyde Park, far from the city's traditional political power bases.

"He grew up an Italian kid in an Irish city and he grew up in a neighborhood that no one came from," said DiCara.

Menino's departure will create only the second open mayoral election in the last half century and the first since 1983, when Kevin White chose not to seek re-election.

Boston City Councilor John Connolly had already indicated his intention to run. Other potential candidates include state Rep. Martin Walsh, city councilors Tito Jackson and Rob Consalvo, state Sen. Sonia Chang-Diaz, and Suffolk District Attorney Daniel Conley.

Menino became acting mayor when his predecessor, Raymond Flynn, left office in 1993 after being named ambassador to the Vatican. Menino, then president of the City Council, was automatically elevated to the mayor's job.

The circumstances prompted some critics to label him the "accidental mayor." But he was elected mayor in his own right in November 1993 and won re-election by wide margins in 1997, 2001, 2005 and 2009.

James Brett, a former state lawmaker who was the Menino's first mayoral opponent in 1993, said he immediately recognized Menino's tenacity as a campaigner.

"Anyone who would underestimate him would be foolish to say the least," said Brett, who now runs the business-backed New England Council. "He was grounded and focused as a candidate."

Peter Meade, director of the Boston Redevelopment Authority, said Menino had an "unbelievable" work ethic, often making two or three more stops around the city after most of his staff had gone home.

While a demanding boss, Meade said Menino "never asked anyone to do anything he wasn't willing or anxious to do himself."

Menino earned the nickname "Urban Mechanic" by focusing on the nuts and bolts of city management – fixing potholes, cleaning streets, and even discouraging the practice of saving a shoveled-out parking space by putting folding chairs or trash cans along the curb.

More recently, Menino became a prominent voice for stricter gun control measures, joining New York Mayor and Boston-area native Michael Bloomberg as co-chairs of Mayors Against Illegal Guns.

"He will be remembered as one of the most influential and important mayors in Boston's long history, and – it is my fervent hope – someone who began to turn the tide against the scourge of gun violence in this country," Bloomberg said in a statement.

Menino also built an impressive political machine that handily defeated challengers and propelled allies into office.

Despite his political savvy, Menino was also known for his sometimes tortured phrases and malapropisms, which earned him the nickname "Mumbles" from detractors but endeared him even more to the populace.

He once confused former New England Patriots placekicker and Super Bowl hero Adam Vinatieri with former Red Sox catcher Jason Varitek and referred to Celtics point guard Rajon Rondo as "Hondo," which was the nickname of former Celtics great John Havlicek.

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