LOS ANGELES, MAY 30 -- California Attorney General John Van de Kamp today unleashed what may be his last major weapon before Tuesday's Democratic gubernatorial primary -- a television commercial in which Ralph Nader describes his opponent, former San Francisco mayor Dianne Feinstein, as "a Republican in Democratic clothing."

Van de Kamp campaign chair Barbara Y. Johnson showed the 30-second spot to reporters this afternoon and said all other commercials for Van de Kamp, who trailed Feinstein by 2 percentage points in a recent Sacramento television station poll, would be pulled to make room for it.

Consumer advocate Nader's reputation for influence over the California electorate assumed legendary proportions in 1988 when an insurance reform initiative he sponsored, Proposition 103, beat four competing initiatives -- including the Feinstein-backed Proposition 104 "no fault" initiative -- despite a $70 million campaign against the Nader initiative by the insurance industry.

The Van de Kamp commercial, to begin running tonight, uses four remarks Nader made during a news conference in Washington Tuesday:

"Attorney General Van de Kamp, . . . he's been very, very critical of insurance industry excesses and has defended insurance consumer rights."

"Dianne Feinstein supported Prop 104, which was the number one priority of the insurance industry."

"If Feinstein and {presumed Republican nominee} Pete Wilson are elected, you might as well send a check to Aetna and State Farm."

"Because she really is a Republican in Democratic clothing."

The last words on the screen are: "Van de Kamp -- The Real Democrat."

Feinstein campaign consultant Bill Carrick called the Nader charges "overdrawn caricatures" and accused Van de Kamp of "hiding behind Ralph Nader." Van de Kamp, he said, "has got to show he is a real live three-dimensional human being to win this nomination."

Johnson said a camera crew from Doak, Shrum and Associates, the Washington-based political consultants working for Van de Kamp, attended the news conference after seeking and receiving permission from Nader. "But we did not know what he was going to say," she said.

Laura Mecoy, a reporter for the McClatchy newspapers who attended the news conference at Nader's Washington office, said it had been expected Nader would discuss the race for California insurance commissioner, a new elected post created by Prop 103. Nader did rate the commissioner candidates, but refrained from endorsing Conway Collis, the candidate backed by Prop 103's Voter Revolt organization, and instead spoke most strongly in favor of Van de Kamp.