A Republican primary loaded with southern California conservatives brought victory to a moderate northern Californian, Rep. Edwin V.W. Zschau, who appears to pose the greatest threat ever to Democrat Alan Cranston's U.S. Senate seat.

After three election victories over ultraconservatives with little appeal to the political middle, Cranston now faces a 46-year-old Silicon Valley entrepreneur who opposed the MX missile and supports the "pro-choice" side of the abortion issue. Zschau (the Z is silent in this German name) beat conservative television commentator Bruce Herschensohn 37 percent to 30 percent in Tuesday's primary, with Los Angeles County Supervisor Mike Antonovich getting 9 percent and Rep. Bobbi Fiedler and state Sen. Ed Davis, 7 percent.

If the Republican field had offered only one or two well-known conservatives, Zschau, who registered just 3 percent in a statewide poll 10 months ago, might have lost. But the crowded field, plus the power of television advertising in California politics, carried the day for him. Zschau spent about $3 million and, long before any other candidate, began running slick commercials throughout the state emphasizing his youth and business experience.

That seemed to more than make up for his absence at candidate forums, where his relatively liberal voting record made him a conservative lightning rod, and for his habit of bursting into occasionally off-key song at campaign appearances.

Zschau said he plans to raise $10 million to beat Cranston and is certain to get heavy national GOP support because of the race's importance for control of the Senate. He applauded Herschensohn's quick endorsement and said, "This sends a strong signal that we in the Republican Party are going to be unified in this race."

Cranston campaign press secretary Kam Kuwata said the 71-year-old senator, who took 81 percent of the vote against token opposition Tuesday, had raised $5 million and expects to raise $5 million more.

Kuwata said Cranston will launch a television campaign this week with taped endorsements from Democratic Sens. Edward M. Kennedy (Mass.), Gary Hart (Colo.), Sam Nunn (Ga.) and Joseph R. Biden Jr. (Del.) Another commercial will dwell on Zschau's stand on the Superfund toxic waste cleanup plan and his switch from opposition to support for aid to anti-Marxist forces in Nicaragua. Kuwata said the Cranston message will be "Don't be confused. We're not electing a commercial here. We're electing a United States senator."

By a surprisingly wide 62 percent to 38 percent vote, Californians approved Proposition 51, an initiative limiting some "pain and suffering" damage awards with the intent of making inexpensive liability insurance easier to obtain. The measure, heavily backed by the insurance industry and local governments, marked the first significant national test of voter sentiment on the much-publicized insurance crisis.

California's election turnout Tuesday was 40 percent of registered voters, the lowest since August 1928. The ballot held only a few hotly contested races and most of the results were expected.

Former city council member Maureen O'Connor became San Diego's first female mayor and will fill the unexpired 2 1/2-year term of Roger Hedgecock, who resigned as head of the nation's eighth largest city after being convicted of conspiracy and perjury.

Republican Mike Curb and Democratic incumbent Leo McCarthy will vie for lieutenant governor in November. Democrat Gray Davis and Republican William Campbell became the nominees for state controller. Comedian Bob Hope's son Tony lost a congressional primary race and a last-minute write-in campaign apparently stopped a follower of Lyndon H. LaRouche Jr. from winning the Democratic nomination for an Orange County seat in Congress.