For decades, Republicans who won statewide office in California found success, at least in part, by showing sensitivity to voters’ commitment to protecting the environment. But with state unemployment hovering at more than 12%, the two GOP candidates at the top of the ticket this year are betting that voters’ concerns about jobs and economic uncertainty will trump any desire for environmental crusades.

Republican Senate nominee Carly Fiorina has spent months charging Democratic incumbent Barbara Boxer with driving an extreme environmental agenda instead of tending to jobs. She has been sharply critical of national and state climate change legislation — deriding Boxer’s concern as being about “the weather” — and has argued that the state should expand oil drilling off its shores.

Gubernatorial nominee Meg Whitman has been more equivocal than Fiorina, but she also has cast the state’s landmark climate change measure as one that kills jobs. She favors delaying its execution for a year to allow further study of its effect.

With those positions, both women are eschewing the strategy that Republicans have used for years to make inroads with Democrats and “decline-to-state” voters, sometimes called independents or nonpartisan.

Former Gov. Pete Wilson championed wilderness protection among other environmental measures as a U.S. senator. During his 1990 gubernatorial campaign, he aired television commercials touting his fight against offshore drilling. Gov. Arnold Schwarzenegger put his Democratic opponent on the defense by fashioning himself as a “green” Republican and signing the climate change bill, AB 32, in the midst of his 2006 reelection campaign. The two men are the only Republicans to have won top statewide races since the 1980s.

“There’s a long history of Republicans in California using the environment to moderate themselves,” said GOP strategist Adam Mendelsohn.

Some Republican consultants have argued that environmental concerns have receded as California’s economy has soured and that Brown and Boxer might risk a backlash if they attack their opponents on environmental issues.

But Mark Baldassare, president of the nonpartisan Public Policy Institute of California, said a new poll by his organization shows Californians’ level of concern has held steady over the last year. In fact, the oil spill in the Gulf of Mexico has “raised the saliency once again of environment issues in California,” he said. “People have factored in that we’re in a weak economy,” Baldassare added. “Even in that context, environmental protection is very important.”

The longtime test of environmental moderation among California Republicans — the “holy grail” as Mendelsohn called it — has been offshore drilling.

Opponents of drilling have generally outnumbered proponents in California over the last 25 years. The results reversed in 2008, when gas prices spiked above $4 a gallon. But the survey released Wednesday by Baldassare’s institute shows that opposition to offshore drilling has shot back up in the wake of the spill in the gulf .

Fifty-nine percent of California voters now oppose more offshore drilling in California, up from 43% last July. Support for more drilling has fallen to 36% from just over half a year ago, the poll found. Those results show the same trend as a Los Angeles Times/University of Southern California College of Letters, Arts & Sciences poll from May — shortly after the blowout of the BP oil well in the gulf — which showed Californians opposed to further offshore drilling by 48%, with 41% in favor.

This year, another litmus test has emerged: the state’s global warming measure, which is under fire from a ballot measure backed by oil companies, Proposition 23, which would suspend it until unemployment drops to 5.5% for at least a year.

Despite Whitman’s and Fiorina’s criticisms of AB 32, support for the law requiring the state to reduce greenhouse gas emissions to 1990 levels by 2020 is about as strong as it was last year — 67%, according to the institute’s survey.

Pollsters did not ask specifically about Proposition 23, but opinion was more mixed when respondents were asked whether the state government should take action its plan to reduce greenhouse gas emissions “right away” or when the state’s economy improves. A little more than half of respondents said the government should take action “right away” while 42% said it should wait. Likely November voters were split evenly.

The new polling numbers, particularly on drilling, could forecast trouble for Fiorina. She and Boxer have volleyed constantly over environmental issues. Fiorina has framed her views as a defense of small businesses, which she says are being swallowed up by state and federal regulations.

When asked in early June whether she would have to pivot to appeal to environmentally minded voters this fall, Fiorina said it was clear that voters’ priorities had shifted: “It’s not that people aren’t concerned about the environment. It’s that they have come to a place that says we’ve got to be sensible about this,” she said.

While Boxer touts both the state and federal climate change legislation as jobs-generating policies — a central theme of her campaign — her opponent has slammed the federal climate change bill Boxer helped craft as “a huge job-killing piece of legislation.”

Fiorina has called AB 32 a “disastrous law.” And though her spokeswoman insists she has not taken a position on Proposition 23, she has often left her listeners with the impression that she supports it.

The state law, she said in a late June appearance on CNBC’s “Closing Bell,” “has killed jobs, so much so that there is a bipartisan effort to have that law suspended until unemployment reaches 5%.... If that isn’t an admission that legislation can kill jobs, I don’t know what is.”

A study by the state’s legislative analyst’s office, which was cited by the Fiorina campaign, said although the effect on jobs could be negative in the short term, the overall effect was mixed and difficult to predict.

So far, the institute poll indicates that Californians are more likely to take Boxer’s side on the jobs argument: 45% said the state’s action on global warming would create more jobs; 23% said it would produce fewer jobs and 24% said they did not expect it to have any effect.

Boxer has described Fiorina’s positions as “radical” and “anti-science.” The senator also has relished the opportunity to describe Fiorina as part of former Alaska Gov. Sarah Palin’s “drill, baby, drill” camp.

Whitman has carefully staked out more middle ground on drilling and climate change than Fiorina. But she has yet to make the kind of overtures to environmentally minded voters that Schwarzenegger and Wilson did.

In an interview with The Times early last year, she said she was open to new offshore drilling. Later, she said she would oppose any new drilling off the California coast until technology could keep environmental risks close to zero.

In recent weeks, she has seemed to soften her once-harsh critique of the climate law, although she still proposes at least a year’s delay in implementing it.

Last fall, she argued that the law’s mandates would “discourage job creation and could kill any recovery.” In a policy booklet released in March, she cited a widely discredited study that said AB 32 would “cost California businesses more than $100 billion to implement and would destroy one million jobs.”

In Whitman’s newest jobs policy booklet, the reference to the economic study was scrubbed and the section includes mild language stating that the economic effect of the law bears further study.

maeve.reston@latimes.com