For 31 years, Robert W. Healy has been the most powerful man in Cambridge.

As city manager, he has quietly and firmly changed the face of Cambridge from a city of shuttered factory doors to a thriving hotbed of technological innovation and research. Time after time, the City Council has willingly renewed his contract.

Through three decades of skillful maneuverings, mostly separated from the political fray, Healy has weathered municipal ups and downs in his efforts to maintain financial stability and promote human services.

He prides himself on blending conservative fiscal policy with liberal social values. “If you don’t have fiscal stability,” he says, “you aren’t able to provide an array of services.”

Now approaching his 70th birthday, Healy plans to bring his tenure as Cambridge’s chief executive to an close in June 2013.

As Cambridge’s other leaders turn to the task of replacing Healy, the city has begun to take inventory of the ingredients that made the longtime city manager so effective.

GOVERNMENT WITHOUT THE POLITICS

In Cambridge, the elected City Council hires a city manager, who oversees almost every facet of the municipality.

Since 1940, there have been seven city managers. In the 15 years preceding Healy’s appointment as manager, the average tenure for a manager was just under three years.

Yet over a period almost ten times as long, Healy has made remarkably few enemies.

“Most people that live in Cambridge are grateful to live in such a great city,” says Kathleen L. Born, a former Cambridge City Councillor. “And there’s no way to separate the city from the city manager.”

Carl F. Barron, who for many years served as the president of the Central Square Business Association, lauds Healy’s performance on the job.

“I think that he’s a top-notch, capable executive who is going to be very difficult to replace,” Barron says.

Talk of Healy’s success as the city manager is widespread, but some citizens have complained that the manager—who according to the Boston Globe makes more than twice as much as the next-highest-paid municipal manager in the state—is not worth the hefty cost of keeping him around. According to a report prepared by Cambridge Day and the Initiative for Investigative Reporting at Northeastern University, he made $336,317 in 2010.

Others are critical of the way he handled the years-long controversy over the firing of Malvina Monteiro, a city employee who claimed she was wrongfully terminated by Healy for complaining about racial discrimination on the job.