Cambridge voters go to the polios next Tuesday with the chance to change the way they cast their ballots--and probably the very nature of the City's politics.

This City of 107,000 is the only one in the nation to vote under a system called Proportional Representation (PR). At one time or another, PR was used in 22 municipalities across the country. New York abandoned it in 1949 (though recently there has been agitation for its return), Cincinnati in 1957, and Hopkins, Minn., in 1961.

In Cambridge, PR was adopted along with the City Manager form of government in 1941, and since then has been unsuccessfully challenged at the polls four times.

PR is extraordinarily complicated--one of the main arguments of the anti-PR force's is that few voters understand the system. "They've been using it for 24 years and still don't know what it's about," says Lawrence Brennan, who is leading the fight against PR.

Its supporters claim, however, that PR's great asset is that it enables different minority groups to gain representation roughly equal to their strength. Thus, on the present Cambridge Council there is one Italian-American, one Negro, and one Jew.

Majority Rule

Opponents of PR insist that the system exerts a permanent divisive influence on the City. Instead of a coalition of interests, the majority ought to rule, they say. What they propose to replace PR with is the traditional non-partisan system of citywide primaries and general elections. In the primary the 18 candidates receiving the highest totals would be nominated for the general election; of these, nine would win in November.

Under PR there are no primaries. Briefly, the system works this way:

A voter lists the candidates in a preferential order (1.2.3...etc.)--this ranking is the crux of the whole system. A voter may list as many candidates as he wishes as long as there is a clear preferential order. The ballots are then distributed into piles according to those who have received the "number one vote" on each blank.

On the basis of the total vote, a quota needed for election is determined (it is one tenth of the total plus one). Some candidates can meet the quota from their "number one" votes. They are declared elected and any ballots they have in surplus of the quota are re-distributed to those who are listed second on the ballot (those who have received the "number two votes"). At the same time, those with the least number of "number one votes" are declared defeated and their ballots are given to those second on the list. This process of elimination and redistribution continues until nine candidates have received the necessary quota.

The technical operation of PR strongly influences the day-to-day workings of politics in the City. Because any successful candidate needs only about ten per cent of the total vote to be elected, his campaign is likely to be relatively restricted--even though voting is city-wide. In practice, City Councillors (and aspiring candidates) concentrate their attention on narrow geographical or interest groups--minority groups, or special professions or occupations.

This style of politics is highly personalized. The skillful councillor has a firm grasp on his "number one votes," and election-time does not see the swaying of large numbers of people from one candidate to another. At a recent political rally, one politician surveyed the crowd and commented: "There's not a person in this room who doesn't already know who his 'number one vote' is going to. You can't be active in Cambridge politics and stay uncommitted."

If the City's voters reject PR next week, Cambridge politics is in for a long and important transition. At first, most politicians seem to agree that the noticeable changes will be few. The same faces will be around, and most will be able to make, at least, a temporary accommodation to the new system.

Effects of Change

But after one or two elections, the effects of the change will make themselves felt. Initially, prospective candidates will find it easier to break into the Council. No longer will a Councillor be able to rely on a small block of faithful, reliable voters. To win he will need a majority. It is the implications of this simple truth that puzzle so many observers.