When City Councilor Kevin Crane '73 announced earlier this week that he would not seek re-election, he dramatically altered the balance of a race that already seemed unusually unpredictable.

Crane's retirement--"I want to devote full time to the practice of law," he said--would seem to give the liberal Cambridge Civic Association (CCA) its best chance in several elections to gain a five-seat majority on the nine-member panel.

The CCA will field seven strong candidates--incumbents David Wylie, David Sullivan, Saundra Graham, and Mayor Francis H. Duehay '55, former city councilor Mary Ellen Preusser, current school committee member Alice Wolf, and well-known State Senate candidate Wendy Abt. The more conservative Independent block will probably be led by four incumbents--Walter Sullivan. Thomas Danchy, Leonard J. Russell, and Alfred E. Vellucci--and a former councilor, Daniel Clinton.

For the more loosely allied Independents to prevent CCA control of the council, all five of their top candidates would have to win, but the odds againsst them may be made even longer because of the city's peculiar voting system.

In proportional representation elections like the one that will take place on November 3, a strong slate is helpful to every member because voters rank candidates in order of preference. As candidates are climinated, votes cast for them "transfer" to the candidate ranked next on the ballot.

And since a much higher percentage of CCA than Independent "number one" votes usually transfer to other members of the slate, a strong lineup that will draw CCA voters to the polls might be enough to give the liberals a fifth seat.

But many, including several Independent candidates, say they think there are simply not enough CCA votes to alter the balance. "It'll be closer than usual, but it won't be different when everything gets added up," one former Independent councilor said. "All those people draw on the same voters, and there are only so many people in West Cambridge (a CCA stronghold)."

And some within the CCA have said in recent weeks that controversial efforts by David Sullivan to clamp down on condominium conversions in the city could anger some traditional CCA voters. "I may lose some support, but I think I'll pick some up too." Sullivan said, adding that his fundraising efforts are ahead of his 1979 pace, when he was one of the biggest spenders in the campaign.

All four Independent candidates are seen by most observers as likely to win, as are CCA incumbents Sullivan, Graham, and Duehay, who, as mayor, may have broadened his base of support to parts of the city where CCA candidates usually draw few votes. Liberal challenger Wolf, who gained a record vote total on the School Committee ballot in 1979, is also heavily favored to pick up a seat.

In the balance may be the ninth seaf and Wylie's reelection chances. The low man on the CCA totem pole in 1979. Wylie is cast as a likely fifth-finisher among state liberals this time around, although even if the CCA gains the seat, he may have to fight Abt and Preusser for its possession.

One potential spoiler, Alvin Thompson, may be joined by others in the weeks before August 21, when nominating petitions must be returned. And, as one political veteran pointed out. "There is more than enough time between now and November for this thing to change in half a dozen different directions. Still, Crane's departure and the strong field of CCA nominees will focus attention for the next four months on the battle for majority control of the council