He's the city's proverbial son. And with his dark suit, clean-shaven face and shiny black shoes, he's a son any parent would be proud of.

Following in a long and influential line of Sullivans on Cambridge's City Council, Michael A. Sullivan was re-elected to the council for a fourth term last week, finishing in the fourth of nine spots.

The year he was born, Sullivan's father Walter, later a Cambridge mayor, ran for the council.

Ever since then, lifelong Cambridge resident Michael, 40, has been involved in city politics in one way or another.

When he was elected to the council in 1993, for example, he got the appointment--unusual for a first-time councillor--to be chair of finance and city safety (a post he still holds).

"After spending my life growing up in the body, I already had a working knowledge of it," Sullivan says.

Sullivan says the city's affordable housing efforts need to provide for middle-income residents as well as low-income tenants.

"We have to be careful...not to lose the middle ground," he says in a deep, calm voice. "Otherwise we become a city of the very very rich and the working poor."