OPENING NIGHT FOR A dance show featuring 80 Cambridge school children was crazy enough without proud parents trying to work their way into Sanders Theater to catch a sneak preview. As the children practiced dance routines on stage with Harvard undergrads, one rosy-checked man managed to slip past my careful eye and quietly poked his head inside.

What could I say? Leonard J. Russell was the city's mayor. And he had given up his Sunday evening just to make a special proclamation declaring the following day "CityStep Day" in Cambridge.

Pausing beside rows of wooden benches, Russell watched with delight, almost envy, as children from four different public schools acted out familiar urban scenes. Only later did I realize how unusual it was for a politician to be mingling with schoolkids in the midst of an election year with several hundred ticket-holding voters waiting in the hallway.

But that was Lenny Russell.

About two months prior to that evening. I talked with Russell in his city hall office about his first year as the highest elected official in the city.

"I love kids. I love to go into the schools several times each week and talk with the children. They really make the job worthwhile," Russell told me.

And even afterwards, when CityStep was having some financial difficulties, Russell proposed setting up a matching fond in which the city would match Harvard dollar for dollar in contributions for the kids' show.

But all those kind intentions came to a halt last week. With just five months left in his first term as mayor of Cambridge--the culmination of this five-term city councilor's career--Russell ended his tortuous bout with throat cancer last Sunday night and died a youthful 52.

A HUSHED CROWD OF mourners overflowed onto Huron Ave. from the west Cambridge funeral home last week to say farewell to one of the city's life-long residents and most dedicated public servants.

Political adversaries and old campaign workers, Cambridge cronies and city hall shakers, St. Peter's Church parishioners as well as local firemen all came to pay tribute to the man whose first name alone appeared on election bumperstickers in the parking lot. From each corner of this diverse city. Lenny's friends came to honor "everybody's mayor, everybody's city councilor."

Lenny Russell never claimed to be a silver-tongued orator nor a Tip O'Neil like parliamentarian. During the 1983 municipal election, the former waste disposal manager told The Crimson that he was just "neighborhood-oriented."

In a city like Cambridge--where high-tech firms are gobbling up every inch of residential land and where the Archie Bunkers are gradually being pushed out by gentrification and the universities--being "neighborhood-oriented" is no easy task.

Labelled an independent on the City Council, the late mayor represented his traditionally blue collar, conservative neighbors for 10 years, but not without paying a price.

"He lost three elections in a row," says Russell's oldest friend Ed Goode. "When you lose three times like that, you get the idea. But not Lenny. We'd shake hands and pound the pavement harder."

Friends say that becoming mayor was the thrill of Russell's life and that he wanted to hold the position for another term.