Only a year after the assassination of Mayor George Moscone, the board liberal coalition he brought together in this city is in a state of disarray and could lose its control of City Hall in Tuesday's mayoral election.

The race pits liberal Democratic Mayor Feinstein, who took office after Moscone was slain last December, against conservative City Supervisor Quentin Kopp, also a Democrat. A decided underdog only a month ago, Kopp has now pulled even with Feinstein by most accounts, and may be on the verge of defeating her and the coalition of liberal activists, minorities and gays she inherited from Moscone.

Feinstein was forced into Tuesday's runoff with Kopp when a low voter turnout in the primary cut deeply into her liberal base of support, and she and Kopp ran virtually even at the polls.

Part of her showing, political observers say, can be blamed on her rather prosaic performance, which has failed to move the city's often fickle liberal population.

"I don't think she has a clear image as an elected official the way George Moscone did as a liberal leader, explains one prominent Feinstein supporter who asked not to be named. "When you get down to it, the people who stayed home during the last election didn't see a lot of difference between her and Kopp."

Kopp's campaign had centered on attacking the city's precarious financial situation, including a projected $117 million municipal deficit next year and runaway costs in the city's retirement system. While his fiscal conservatism has won him support of the city's moderate middle classes, Kopp also has benefited from several key liberal defections from the Feinstein campaign.

Kopp has garnered endorsements from a number of leaders in the city's black and Hispanic communities, as well as from San Francisco's more liberal newspapers, the Chronicle and Bay Guardian. The Examiner has endorsed Feinstein.

Even more crucial are the inroads Kopp has made in the city's politically potent gay community, which is miffed at Feinstein over her ousting of liberal police chief Charles Gain last July. While Feinstein narrowly won the endorsement of the city's two gay Democratic clubs, Kopp has been supported by all three of the gay community's newspapers.

Adding to Feinstein's problems are predictions of another poor turnout at the polls Tuesday.

"There's a lot of disillusionment and malaise about the whole political structure," said Corey Busch, former press secretary to Moscone.

"I really believe that she [feinstein] suffers from the residues of the assassination," Busch said. "Those who were Moscone's supporters are still trying to shake the effects of that, and a lot of them have just decided the hell with it." CAPTION: Picture, MAYOR DIANNE FEINSTEIN . . . hurt by defections from campaign