The exit of two incumbents from the 1989 City Council election has led possible candidates to begin jockeying for support more than a year in advance.

Last week, City Councillors David E. Sullivan and Saundra M. Graham announced they would not seek re-election next year. Both are members of the pro-rent control Cambridge Civic Association (CCA), and their withdrawal could leave the Council open for a possible shift in its balance of power.

For the past four years, the same nine members have been all but stalemated. There have been four CCA members, four more conservative, neighborhood-oriented Independents, and Alfred E. Vellucci--now the Mayor--who votes with the CCA on housing policy and with the Independents on many other issues.

Several political observers said many candidates were frustrated by the 1987 election results, which left all nine incumbents seated.

Observers say a shift from this pattern could pave the way for a change in the city's rent control policies.

"Prime contenders" for the open seats include CCA member Jonathan Myers and Edward N. Cyr, according to City Councillor Sheila T. Russell who, like them, lives in North Cambridge.

Although Cyr ran as an Independent in last year's election, he said he supports many of the CCA's goals. In that election, Myers and Cyr came in 10th and 12th, respectively, in a race for nine seats.

Russell said last night she "had a feeling" the candidates are already trying to gather support for next year's election, adding there was much speculation on who will take Sullivan and Graham's seats. If unknown candidates were to gain the seats, she said, they are likely to be different from current Councillors--"a little more conservative than the liberal CCA, [but] not the old guard."

However, Russell said, "anyone new would have to be a real flash--someone who gathered a lot of publicity fast."

Asked about possible candidates to replace Graham and Sullivan, Vellucci said he "could care less who's running."

"I could care less if David Sullivan or Saundra Graham comes or goes, the City of Cambridge will go on," he said.

"You'll see some candidates come out of the woodwork," said Myers. "There's been a lot of speculation about it."

Myers also called the vacancies "slightly enticing," and said the city was "ripe for a swing in this political direction," referring to the CCA.

Cyr, who has said he will probably run for Council, said last night that he was surprised so few candidates had announced they will run next year.

"I can't figure out what it means," added Cyr. "I haven't seen two open seats in my lifetime." Cyr said he was sure there would be a "larger field" by election time.