AFTER LAST WEEK'S elections, Cambridge liberals should be smiling.

After all, candidates from the Cambridge Civic Association (CCA), the city's old-line liberal group, nabbed four of six school committee seats and four of nine city council slots. The CCA vote percentage was much higher than usual. David Sullivan, the CCA's rising star, finished far better than any liberal candidate in history, topping the total necessary for election by more than 200 votes on the first count--an unheard-of feat. A huge new liberal constituency--student voters--turned out for the first time, and about 800 new pro-rent control tenants went to the polls. There was a marked liberal-slate loyalty among the city's voters; if they voted for one liberal on Cambridge's complicated preferential ballot, 90 per cent of the time they would vote for all the liberals.

Yes, Cambridge liberals should be smiling, but they're not. There is very little joy up and down Brattle St. or on the backroads of mid-Cambridge, where city progressives like to hang out. All that money, all that campaigning and all those liberal votes merely maintained the same number of progressives on the council. "No more, no less, we just tread water like every year," a disgusted CCA adherent complained as the final vote totals came in. And that means two more years of dependence on independent Alfred E. Vellucci for the fifth vote necessary to pass liberal programs, notably rent control.

Velluci's support is not likely to waver, although he may demand the mayor's office as a token of appreciation. But when Velluci, the senior member of the council, someday decides not to run again, his decision won't add his East Cambridge constituency to the CCA ranks. The Italian-surnamed successor that Vellucci-supporters are likely to find won't prove as liberal. Instead, a new neighborhood dynasty, like those built by other city conservatives, could rise, toppling the liberal coalition majority and with it rent control.

THAT SCENARIO may be just one of many, but it points to the real need city liberals feel to establish a ruling liberal majority in the next election. Winning that fifth CCA seat won't be easy. To combat the single-minded determination of the city's conservative voters, who often pick their friend's son and bullet vote for him, liberals can choose from two different but compatible strategies.

The first option is to take the conservatives' traditional approach, building up personal coalitions relying on personality and a few wellknown positions as well as on the backing of the ever-powerful CCA. No liberal council candidate has ever run as well as David Sullivan, who appealed in large part to the new voters--students and tenants in particular. Sullivan waged a traditional campaign--pressing the flesh, ringing the doorbells--and he built up a large network of volunteers independent of the CCA. The trend is obvious down the line. Francis Duehay'55, who also ran a high-budget, high-profile campaign, finished stronger than ever before in his re-election bid, only a few hundred votes behind Sullivan. And the candidate who relied most on old-line liberal CCA connections, Mary Ellen Preusser, finished last, losing badly in her re-election bid.

There is inherent danger in emphasizing personal tactics to the exclusion of the CCA. Under Cambridge's proportional representation system, the second preference votes often turn out to be crucial in deciding the last few council seats--for many years they gave the CCA a fourth seat. If personal dynasties become too powerful, unschooled liberal voters might bullet-vote regularly, robbing the progressive slate of support. This year's experience indicates that that problem can be overcome, however. Sullivan, who explained to voters in person and on his literature that a vote for him had to be backed up with a vote for the slate, watched election workers distribute more than 90 per cent of his surplus ballots to other progressive candidates.

Appealing personally to voters will require more than a conscious decision, however. Strong candidates must be found, personalities voters can develop a fondness for. Sullivan may fit that bill, as may School Committee member Alice Wolf, who piled up city-wide support and a record number of votes in her school board bid. If a strong attachment, personal perhaps, to one candidate can be combined with a weaker intellectual support for other progressives, the CCA may have found a new tactic.

The other option, which could be pursued at the same time, is to beef up the CCA slate effort. The CCA has been tainted almost from its birth 40 years ago by the support of the wealthy few. Even today, it is common to hear complaints about the Brattle St. crowd running the city, about newcomers governing the CCA. The group must shed that image to establish a base in conservative and ethnic districts of the city, especially East Cambridge.

ONE WAY to shake the elitist label is to disguise the CCA a little, to change its focus from a good-government "progressive" group to one that simply takes liberal positions on the big issues of the day. In this election, everyone was talking about rent control and condominium conversion; the CCA should have focused on those issues more strongly in its literature. At the very least, old-line CCA members should swallow their pride and return to the "Cambridge Convention" label adopted years ago. Hiding the CCA name probably won't mystify supporters, but it may calm those in other parts of the city who support the group's position ideologically but can't bring themselves to back the upper crust.

Increasing slate loyalty among black voters is another way the CCA could improve its electoral performance. Three black candidates--Saundra Graham. Alvin Thompson and Severlin Singleton--ran for council this year. Only one, incumbent Graham, was elected. The second-choice votes on the ballots cast for all three tended to be for one of the other black candidates. Often voters chose the three blacks and didn't bother to vote past that. How to pick up stronger slate support from black voters is a tricky problem, but one the CCA must address if it wants the few hundred votes that could make the difference between four and five seats in the next election.

And five seats would make the CCA really happy. There is plenty of reason for jubilation among Cambridge liberals this week--they did better than ever before. But the biggest party will come the day the CCA captures five seats on the city council.