DEFECTION" and "Sell-Out" are words commonly heard in City Hall these days. The reason is simple: the traditional lines that divided Cambridge politicos into two camps, the independents and the liberals, have weakened this spring.

Animosities among city councilors have intensified and each city council meeting brings a new round of mudslinging.

After last year's election, the council looked like it would be a tight organization dominated by a five-man independent majority. The regime of former mayor Barbara Ackermann and her liberal Cambridge Civic Association (CCA) colleagues would be replaced by the likes of tough Alfred E. Vellucci and fast-talking Walter J. Sullivan.

But in January an unexpected battle for the mayoral post among the council's five independents led to the first major break within the group. After 30 ballots and a month of bickering, Walter Sullivan won the job, but not before making a classic political deal with the liberals.

Sullivan, who served as mayor for two years (1968-69) and who is the city's top vote-getter, solicited liberal support in his mayoral bid in return for support in his mayoral bid in return for support of the liberals' move to replace City Manager John H. Corcoran.

Corcoran was a friend of the independents, especially during the two years (1970-71) when the independents last controlled the council, during Alfred Vellucci's term as mayor.

Joining Sullivan in the deal with the liberals was freshman councilor Leonard J. Russell, who subsequently won the election for vice mayor.

Extremely angered by the outcome of the mayoral election, independent Thomas W. Danehy accused Sullivan and Russell of "selling-out to the CCA." Fellow independents Vellucci and Daniel J. Clinton were also upset but less vocal.

Danehy had campaigned for the mayor's office, arguing that he was next in line for the post. Sullivan and Vellucci were the last independent mayors. Councilors Clinton and Russell lacked enough council experience to claim the office, Danehy said in January.

Now Danehy remains bitter over Sullivan's affair with the liberals and has repeatedly tried to break up the romance with attacks on several fronts. He already has introduced a measure before the council to abolish the controversial rent control board in Cambridge. The three CCA councilors and Saundra Graham of the radical Grass Roots Organization defeated that measure with votes from Sullivan and Russell.

Danehy then tried to delay the appointment of Lowell City Manager James L. Sullivan as John Corcoran's successor at City Hall. To Danehy's amazement, Corcoran neither contested his dismissal nor called public hearings and the council majority followed through with Sullivan's appointment.

The city manager's salary then became an issue with which Danehy sharpened his attack on the council coalition. One the same March evening when the council voted to appoint James Sullivan city manager, the council raised the manager's annual pay from $34,000 to $45,000. Danehy called the pay hike "the most brazen political act ever taken in this city," and charged that the coalition raised the manager's salary prior to John Corcoran's April 1 retirement in order to increase Corcoran's pension.

Danehy also alleged that the council coalition had bargained with Corcoran, promising the pension increase, in return for his resignation without a fight.

"In order to get Mr. Corcoran to retire without having to fire him, the councilors told him they'd sweeten up his pay," Danehy said.

Independent Clinton, Danehy's closest friend on the council, said the raise "couldn't have come out of thin air. There must be some reason why a man who is about to be fired would not go through the usual hearings."