LOS ANGELES, JUNE 5 -- Former San Francisco mayor Dianne Feinstein tonight became the first woman to win a major party primary for governor of California.

With just 18 percent of votes counted, Feinstein, who once trailed state Attorney General John Van de Kamp by 18 percentage points in the polls, led by 51 to 41 percent. Nine other candidates split the remainder of the vote, and Van de Kamp conceded less than three hours after the polls closed.

"Diane. . . I will be working on your behalf to make history," he said.

"Well, we did it," Feinstein told a cheering crowd of supporters. "One mission completed and one to go."

Feinstein faces what is expected to be a difficult and expensive campaign against Republican nominee Sen. Pete Wilson. He appeared to accept the result early, challenging Feinstein to several debates less than two hours after the polls closed at a celebration of his expected primary victory.

Feinstein was favored by supporters of abortion rights and the death penalty and lost to Van de Kamp only among voters who emphasized environmental issues, exit polls by Los Angeles television station KABC said.

Exit polls showed an initiative called Proposition 111, closely watched in Washington as an indication of voter feelings on new taxes, was leading narrowly, 52 to 48 percent, with about 10 percent of the votes counted. The proposal would loosen state spending limits and raise the gasoline tax by 9 cents per gallon to fund $18.5 billion in transportation improvements. A related rail transportation initiative was leading 54 to 46 percent.

Some of the most controversial campaign commercials were directed against two redistricting initiatives, Propositions 118 and 119, which were supported by Republicans eager to remove the Democratic-controlled legislature's power to apportion seats after the 1990 Census. Both initiatives were losing by about 20-point margins in early returns, after a $3 million Democratic publicity barrage labeled them "voter fraud."

Projections indicated Proposition 115, streamlining the state criminal justice system to match federal rules, would pass easily.

State vote-counting computers broke down after the first small run of votes were counted, leaving several other races in doubt. Republican State Sen. Marian Bergeson was projected the winner of the GOP lieutenant governor primary by one Los Angeles station. State Sen. John Garamendi was leading in early Democratic primary returns for insurance commissioner and San Francisco district attorney Arlo Smith was leading in the Democratic primary for attorney general, although Smith's opponent, Los Angeles District Attorney Ira Reiner, claimed victory on the basis of exit polls.

In the Republican primary for state treasurer, appointed incumbent Thomas Hayes had a 2-to-1 lead over former U.S. Treasurer Angela "Bay" Buchanan, sister of commentator Pat Buchanan, in early returns.

Feinstein, 57, nine years mayor of San Francisco, and Wilson, 12 years mayor of San Diego, are centrists who support abortion rights, capital punishment and more state spending on social programs than favored by Gov. George Deukmejian (R), who did not seek reelection. Both have close ties to business interests and are regarded with suspicion by their parties' extreme wings, the left in Feinstein's case and the right in Wilson's.

Their basic differences appear to be party label and gender. Polls show Van de Kamp was handicapped by being male and one Los Angeles Times survey indicated voters this year preferred a woman when all other differences were discounted. Feinstein is expected to appeal again to voters to "make history" by electing her the first female chief executive of the nation's largest state.

Wilson and his much wealthier party may be able to spend as much as $20 million on the race, however, twice what Democrats are expected to raise even with the help of Feinstein and her financier husband, Richard Blum, who spent at least $3 million in personal funds in the primary.

Feinstein overcame a deficit in the polls with a February television commercial that emphasized her dramatic succession as mayor in the wake of the murder of Mayor George Moscone and Supervisor Harvey Milk. Her commercials emphasized not only her stand on women's rights, but her support for the death penalty. Van de Kamp struggled to defend himself as a prosecutor committed to abortion rights and capital punishment, even though they conflicted with his personal beliefs.

Van de Kamp won support by drafting a landmark environmental protection initiative for the November ballot known as Big Green. But Feinstein endorsed the same initiative on Earth Day and is expected to use it against Wilson, who has objected to the initiative's creation of an environmental czar to administer an assault on pesticides, oil spills and deforestation.