Political workers supporting Cambridge Mayor Walter J. Sullivan's bid to become sheriff of Middlesex County apparently broke a state law that forbids campaigning within 150 feet of a polling place on election day.

A spot check of Cambridge polling places showed that Sullivan campaign workers violated the 150-foot limit in at least seven separate instances.

The Crimson survey also showed that dispite a Massachusetts law requiring that law enforcement personnel be stationed at polling places, there were no policemen patrolling at least five polling places in the city.

Sullivan campaign officials said yesterday that their workers had been instructed to abide by the 150-foot limit.

Edward Sullivan, the mayor's brother, said that it was not possible to control the actions of each Sullivan worker. He said that some of the workers may have gone into the polling places "to get out of the weather."

One Sullivan campaign supporter working the polls in the Cambridge Public Library said yesterday he had been told by campaign leaders "to stand where the crowd is" and to mingle with people as they enter the polls.

Election wardens at the seven polling places where Sullivan workers apparently broke the distance rule said they knew of the violations, but that only police could initiate action against the workers.

State law mandates that election officials report any violation of the legal limit to the police, "who shall prosecute violators."

The policeman stationed at the ward, 6, precinct 3 polling place in the Broadway Fire Station said yesterday, "We really don't enforce the (150 feet) rule."

"It's small potatoes," the officer said of the law. "I've never heard of anyone being fined."