Cal Kantor, a former assistant to the Cambridge police commissioner, is a leading candidate to be the next head of Harvard's troubled security service, department sources said.

Reached by phone earlier this month, Kantor confirmed that he is a candidate but declined to comment further. "If I get the job, then we can talk about it," he said.

Cambridge police officials said they could not release details of Kantor's career on the city force. But police officers say Kantor was liked and well-known among police for an unusually straightforward, honest style.

Harvard sources said that at least one other candidate remains for the post. One candidate is rumored to have worked for the Federal Bureau of Investigation.

Herbert J. Vallier, the police department's assistant director for finance and administration, first advertised the post in the Harvard Gazette and in local police departments last month.

He has said he is looking for a candidate with strong interpersonal skills and the ability to manage a contract service like the University's security guard unit.

For two days, the service has been badly divided by charges of racial discrimination and favoritism. The man at the center of many of the charges, manager of operations for security Robert J. Dowling, has left the unit.

A report ordered by vice president and General Counsel Margaret H. Marshall and released in July 1993 cleared the service's management of any discrimination charges. At the same time, the Marshall Report criticized numerous guard unit procedures and made 17 recommendations for reform.

The guard service, which is part of the Harvard Police Department, has also lost contracts with many parts of the University recently. The Law School, the Business School and the Medical School have all contracted with outside security services.