The Massachusetts State Senate yesterday unanimously defeated a bill which would have excluded many Harvard graduate students from the protection of the state Fair Housing Act.

The bill, which many senators considered a step backward for anti-discrimination in housing, specified that rooming houses renting to four or fewer boarders would not be covered by the Housing Act which was passed last year. That act forbids discrimination in the sale or rental of all housing offered publicly, with the exception of the second apartment of an owner-occupied two family house. It is widely considered one of the best such anti-discrimination laws in the nation.

Several senators attributed the bill's defeat to a massive citizen campaign mounted in the past week by civil rights, religious, labor, political and service organizations throughout the state. Members of these groups wrote and phoned all the state senators, the president of the state senate, the governor, and Senator Edward M. Kennedy '54, urging opposition to the proposal.

The defeated bill had a curious history. It was proposed as an amendment to the Fair Housing Act last December by the Mass. Commission Against Discrimination, which apparently feared courts might rule the Act unconstitutional as an invasion of privacy.

In January, the MCAD changed its mind and decided that its proposal would exclude too many renters from protection against discrimination. The Commissioners then petitioned to be allowed to with-draw the bill, but were refused.

On Monday the MCAD took the initiative and wrote to the senators, urging them to defeat its bill. That, in addition to the citizen campaign, apparently did the trick.