Ask any veteran Cambridge political pundit, and he's bound to tell you why this year's race for nine City Council spots is like no other in recent memory.

Although campaign bumperstickers and buttons reveal the names haven't changed much since the 1983 election, they don't mention that the field of candidates has grown significantly from 16 to 22 in two years. The scramble for the city's most coveted political prizes started as far back as last June when the unoccupied seat of a long-time incumbent, the late Mayor Leonard J. Russell, suddenly intensified the pace of a sleepy race.

In addition, young, affluent professionals have mobilized their own coalition of candidates this year, leading both liberal and conservative pols to wonder whether their traditional political bases in ethnic working-class neighborhoods will survive the onslaught of newcomers to Cambridge.

Like past elections, uncertainty is the hallmark of this year's race. No one knows for sure who will emerge a winner out of tomorrow's tally until the final ballots are counted next week. And no observer can begin to assess the impact of those results until November of 1987.

Everything from local housing policy to the choice of the city manager and from city services to crime-fighting rests on tomorrow's vote. If the current balance between liberal and conservative councilors on the nine-member body shifts by a single seat, two years of hard-fought legislation could all be reversed.

Strict rent control--the single most important force in shaping Cambridge's population--could die a quick death. Rampant conversion of low- and moderate-income housing into Yuppified condominiums, a trend characteristic of the 1970's, could take rent control's place. If the council's composition changes significantly, Cantabs could see real estate developers gobbling up more and more of the city's precious land.

At least that's what the incumbents are saying; challengers contend that city voters are calling for some radical departures from past housing laws, city services, and the overall liberal agenda.

Campaign coffers this year reflect the uncertainty felt by the Sullivans and Russells of Cambridge. So far, candidates are spending more than of $12,000 to win a job that only pays $18,000. This year's total financial expenditures exceed $125,000--a figure which is up 25 percent from 1983, proving that candidates are going for broke in the campaign.

The emergence of moderate candidates Geneva Malenfant, Hugh Adams Russell '64, and Karen Swaim--running under the Coalition '85 banner, may upset the balance between the two entrenched local groups: the liberal, Cambridge Civic Association (CCA) which advocates good government and social issues; and the loosely-affiliated, neighborhood-oriented Independents who support constituency services.

There are currently four CCA and four Independents on the council, and City Councilor Alfred E. Vellucci is the self-proclaimed swing-vote.

Because they advocate housing reform, Coalition '85 candidates are seen as nabbing the votes of the city's condominium owners, upper to middle class, college-educated, professional and liberal people who have felt disenfranchised because of the CCA's tough stance on condo conversion.

Partially made up of former CCA members, the Coalition last month released a letter signed by five ex-CCA leaders who charged that their former organization's platform was "rigid and doctrinaire." CCA-backed candidates dismissed the statement and called the signers has-beens in the party.

But for 13 straight elections, Independent City Councilor Walter J. Sullivan has been the top vote-getter, pulling in the most number one votes of any candidate.

Under Cambridge's antiquated system of proportional balloting, voters rank candidates in order of preference--one, two, three and so on. As a candidate reaches quota and is declared elected, his surplus votes are transferred to the candidate ranked second on the ballot. Then, the candidate with the fewest votes is eliminated in successive rounds and his ballots are similarly redistributed. This process continues until all the seats are filled.

Sullivan perennially leads the pack, and his surplus votes usually help elect other Independents like City Councilors Thomas W. Danehy and Daniel J. Clinton. This year's unexpectedly strong showing from Independent challengers William J. Walsh and Sheila T. Russell, who have shown strong neighborhood support and name recognition, are likely to detract surplus votes and may even unseat two incumbents, observers say.

Local pols are also predicting that first-term City Councilor Alice K. Wolf will finish first among the CCA's six endorsed candidates. Incumbent David E. Sullivan, who finished seventh in 1983, is predicted to lose key tenant votes because of his purchase of a home in Cambridgeport and the candidacy of rent control advocate Michael H. Turk. Mayor Francis H. Duehay '55, a twenty-two year veteran politician, is expected to ease into his seat again due in large part to the popularity of his four-month term as mayor.

Three Black candidates backed by the CCA--State Rep. Saundra K. Graham, Kenneth E. Reeves '72, and Renae Scott--are expected to vie for the city's 5000 registered minority voters. As the ballot tabulating progresses, observers say that Reeves and Scott will feed votes into Graham's pile and assure her reelection.

In East Cambridge, 70-year old urban populist Alfred E. Vellucci faces a tough run for the roses against a few of his Independent neighbors, City Councilor Alfred W. LaRosa and Francis Budryk. Vellucci, a three-term mayor who has held a city council seat since 1956, has been targeted by rent control opponents for his support of CCA social issues.

Although the number of registered voters has declined by nearly 5000 this year, three referenda questions on tomorrow's ballot are expected to bring out the feminist vote, Harvard-haters, and North Cambridge residents opposed to nerve gas testing in their own backyards.