In Cambridge, there isn't much in a name.

Three unrelated men named Sullivan are running for the Cambridge City Council this year--instead of the usual two.

Local voters have managed for many years to distinguish between genial, snowy-haired Walter J. Sullivan Jr., and David E. Sullivan, an outspoken advocate of rent control and member of the liberal Cambridge Civic Association (CCA).

But this Tuesday they will have to choose between these incumbents and 26-year-old David J.'s Sullivan, who says he is after a Council seat because of a personal grievance agaist the rent control law.

David E. Sullivan, the incumbent, says David J.'s campaign is a hoary political trick designed to confuse voters, and notes that the history of Boston machine politics offers several precedents.

David E.'s campaign flyers declare that "they'll do anything to get David E. Sullivan off the City Council," and blame David J's candidacy on "the big-time developers, the slum landlords, the patronage politicians, the fast-buck condo converters..."

David J., 26, said his reason for running is the 1979 law that stopped him from buying a rent-controlled unit in his grandfather's house. This "removal ordinance," drafted by David E. Sullivan, bars landlords from converting apartments into condominiums, even by selling them to the tenants.

An apartment can only qualify for removal from the rent-control rolls if the owner occupies it, if the tenant lived there before the cutoff date of August 10, 1979, or if it is in such bad condition that only new construction can make it habitable.

David J. may not buy his own unit because he moved in after 1979 and it is in good shape. So instead of buying the unit as a condominium, he must remain a rent-control tenant of his own grandfather.

This Sullivan argues that rent control imposes hard and often absurd burdens on small landlords, and he supports a system of "vacancy decontrol," which would allow an owner to stop renting a controlled apartment after the tenant left. Supporters of the current system, however, say David J.'s proposal would both reduce the housing stock and encourage landlords to use devious means of getting tenants to move out.

David E. says David J. is running as a spoiler and not because he really wants a Council seat. He notes the 26-year-old challenger's lack of political experience, and says that David J. has not campaigned vigorously.

Whether he wants the Council seat or not, David J. says he doesn't want the money. He has promised that in the unlikely event that he wins a seat, he will give his annual $25,000 salary to a fund for the homeless, with David E. as a trustee by way of "burying the hatchet."

Despite the circumstantial evidence, David E. has not offered specific proof of his charge, nor has he blamed any specific person for David J.'s candidacy. Campaign finance statements show that David J.'s campaign fund, at $1445, is just over a tenth the size of David E.'s, and that no real estate owners stand out among David J.'s contributors.

David J. says he joined the race out of honest anger at the system, and especially at David E., who is behind the 1979 law. "I think he's diverting attention from an unfair housing policy to this name thing," he says of David E.'s reactions.

David J. has used much of his speaking time at campaign forums to attack David E. for both his policies and his accusations of trickery. David E. has avoided comment on any of David J.'s statements.

However, both Davids seem equally eager to avoid confusion. David E.'s white-on-blue bumper stickers show the middle initial in bright red, while the other David's yellow--on--green logo emphasizes a gigantic 'J'. The 'J' stands for Jude, and a disc jockey friend of the candidate's has been playing "Hey Jude" on a local radio station.

Will D. Jude Sullivan make it bad for David E.? The challenger says David E. may lose fewer votes to confusion than he gains by telling constituents that he needs extra help this year because of the attack.

On the other hand, David E. has special reason to be nervous because of the city proportional representation system. It takes only about 2000 votes to elect a candidate, and most victories are by margins of a few hundred votes or less--so even a few cases of confusion could have a large effect.

Mayor Walter Sullivan, who, like David J., opposes rent control, is sanguine about the affect on his own campaign, although he says he has had to "work a little harder."

"I've always had a Sullivan against me," says the mayor--or "if it wasn't a Sullivan it was someone similar to." He says he first ran for Council against an impostor with the same name as his own brother--Edward J. Sullivan. "The CCA did that," he says, noting that he beat Edward J. by 5 to 1.

Despite his experience, the mayor says he doesnot see trickery in David J.'s campaign. "I thinkthe kid believes in what he's doing," says WalterSullivan. "He's a real sincere kid."

As one of the city's most popular figures,Walter Sullivan has little to worry about. He wasthe top vote-getter in the city long before DavidJ. was born, and he has held that position eversince--though his margin has declined slowly inrecent years as traditional voters die or moveaway.

Walter Sullivan campaign signs cover frontyards and windows all over the city. His campaignadvertisement features an endorsement from anotherbeloved Cantabrigian, former Speaker of the HouseThomas P. "Tip" O'Neill, Jr.

Unlike either of the Davids, Walter Sullivan isknown to avoid public speaking. He rarely attendscampaign forums, and his only visiblecontributions to most Council meetings arewell-timed strokes of the gavel.

Sullivan is said to exert his considerablepolitical power in quiet conversations behind thescenes. His campaign goes on at communitygatherings, wakes, weddings and funerals--oftenseveral in a day, the year round. WalterSullivan's declaration of campaign expendituresshows charity donations and florists' bills by faroutnumber the usual payments for bumper stickersor newspaper advertisements.

The mayor's family also contributes to hispopularity. Walter Sullivan's father, the lateMichael "Mickey the Dude" Sullivan, is stillremembered in parts of the city for his generosityto poor families during the Depression. Hisbrother, Edward J. Sullivan, is the MiddlesexCounty Clerk of Courts, and Walter himself holds asecond job as Assistant Clerk of Courts.

Though he is not related to the mayor's family,David J. Sullivan is a lifelong city resident, andshares something of Walter Sullivan's world. DavidE. Sullivan, on the other hand, could not presenta greater contrast.

As David J. indignantly points out, David E.was born in Buffalo, N.Y., and first enteredCambridge politics as a Harvard Law School studentwho discovered that he was not allowed to vote inCambridge. After working to get the vote forstudents, he stayed in Cambridge--and stayed incity politics as a liberal tenant advocate whoopposes university expansion