From Cambridge’s website:

Adoption Of Plan E

On June 1, 1938, Massachusetts Governor Charles F. Hurley signed a bill adding a fifth city charter form (Plan E) to the four plans already available. Modeled after a charter successful in Cincinnati, Plan E provided for a city manager form of government with proportional representation (PR) elections.

As soon as the bill became law, a group of citizens formed the Cambridge Committee for Plan E and obtained the necessary signatures on a petition to put the question of adopting Plan E on the Cambridge ballot in November 1938.

In the ensuing campaign, Plan E advocates said it would mean that a trained administrator and not a politician would run the city. Of PR voting, they said itwould guarantee majority rule and at the same time give minority groups representation in proportion to their actual strength.

Opponents centered much of their fire on the PR voting system, which they said would excite group prejudices and make voting a lottery. They also said the plan would be too expensive and would give too much power to the City Council.

Emotions ran high and , on that electionday in 1938, Plan E was defeated by 1,767 votes. Two years later, it was adopted by 7,552 votes, with a winning margin in eight of the city’s eleven wards. The first PR election was held in 1941 with the first Plan E government taking office in January 1942. Since then, there have been five referenda—in 1952, 1953, 1957, 1961, and 1965—on whether to repeal or retain the PR voting system. Each time the vote was to retain it.