WATCH OUT, Harvard. The City Councilor who once threatened to turn The Yard into a bus station, the very same man who had The Square renamed for Christopher Columbus, is back in charge.

Alfred E. Vellucci begins his fourth two-year term as mayor of Cambridge this month. At 72, he has spent half his life in local politics, earning a reputation for colorful oratory, political cunning and undying persistence in giving come-uppances to the blue-blooded types of Harvard University.

A master politician, Vellucci is one of the few who can stay on good terms with all camps in the City Council, where polarized political opinions often stymie productive compromise.

As Mayor and as a City Councilor, Vellucci has distinguished himself as a spokesman for the individual against the institution. His successes range from public housing starts to a courageous campaign to bar the manufacture of never gas in a residential district of the city, to the extraction of $1.5 million in voluntary payments from Harvard and MIT.

Officially one of the traditional-minded Independents, Vellucci actually belongs to a political party all his own. He is an old-fashioned populist when the issue is trash removal or repairing East Cambridge park benches. But Vellucci has also provided the swing vote for newfangled Cambridge Civic Association (CCA) projects from rent control to the adoption of an El Salvadorean "sister city."

As Mayor, Vellucci automatically chairs the School Committee in addition to his duties on the Council. His progressive views on education are welcome as the School Committee faces contract negotiations and a dispute over parents' role in evaluating teachers.

The new mayor combines the human compassion of the old politics with the progressive social conscience of the new. The result is a man well able to rein in either the business-boosting right or the technocratic left. Al Vellucci is back in charge--the city's in good hands.