Gov. Jerry Brown has taken the national stage to tout California’s fight against global warming, telling cheering throngs at the Democratic National Convention that the state has “the toughest climate laws in the country.” Yet inside the state Capitol, the fate of the policy’s centerpiece—legislation to drastically reduce greenhouse gas emissions—is in peril.

One ominous sign: The Democratic leader of the Assembly has not thrown his weight behind the bill.

“For us, it’s not imperative that it get done this year,” said Anthony Rendon, who has a background as an environmentalist but rose to speaker this year with support from a powerful bloc of business-friendly Democrats. “It’s a program that has had its success, but at the same time there are some corrections that could be made. We just want to make sure that if we’re going to set something up for the long term, that we get it right.”

Senate Bill 32 is shaping up as the biggest fight lawmakers are likely to tackle in what remains of the legislative year. It pits environmentalist Democrats, mostly from the state’s more prosperous coastal areas, against Democrats and Republicans from struggling inland areas who side with oil companies and other businesses, and whose constituents could be harder hit by rising energy prices.

The bill, which sets ambitious targets to cut planet-warming emissions by 2030, faces a critical deadline with the Legislature set to wrap up for the year on Aug. 31.

Sen. Fran Pavley—the Agoura Hills Democrat widely regarded as an environmental champion—authored the legislation to build on a pioneering climate change agenda the Legislature enacted a decade ago, when it passed her Assembly Bill 32. That bill set targets for reducing greenhouse gas emissions by 2020 and led to California’s cap and trade system, which limits how much climate-warming gas businesses can emit while allowing them to buy and sell permits to pollute.

Pavley, now serving her last year in the Legislature, wants to extend the approach further into the future. But the Legislature has changed a lot since her earlier bill passed in 2006—no one currently in the Assembly was in office then—and the lower house rejected SB 32 last year amid intense lobbying by the oil industry.

Failure again this month would indicate a major about-face for the California Legislature, reversing course on the environmental leadership role that Brown routinely boasts of in national and international appearances. It would also mark defeat for Pavley, a maverick in the war on global warming who is leaving the Capitol because of term limits.

“It’s really not about me,” she said, but about the Legislature’s commitment to keep combatting climate change.

“This should be easier to pass this year than it was 10 years ago, because now we can show that putting a cap on emissions and rolling it back does send signals for investment (in clean energy businesses). And we’re seeing those new jobs here in California. We have success stories to tell but the challenge has been that the Assembly, of course, hasn’t been paying close attention because they weren’t here.”

California’s Emissions, Population and Economic Growth

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Sources: California Air Resources Board; California Department of Finance; US Bureau of Economic Analysis. Graphic by Jeremy Rue for CALMatters.

Her effort is backed by a big advertising push from environmental groups. NextGen Climate, headed by San Francisco billionaire Tom Steyer, is spending $1.2 million to air television adsaround the state criticizing oil companies for “trying to weaken our clean air laws.” The California League of Conservation Voters has launched a social media campaign urging voters to contact Democrats who helped defeat SB 32 last year.

“We saw what happened last year,” said spokeswoman Jenesse Miller, “so this year going in we knew we were going to have to ask those lawmakers to do the right thing and vote the way their constituents want.”

Recent polling found that a majority of Californians support reducing greenhouse gas emissions, even if it means paying more for gas and electricity.

But businesses that use lots of electricity say their costs have already gone up too much—and they fear SB 32 will trigger continual increases without enough oversight from legislators.

“When we’re moving from 2020 to 2030, we need to understand what the policies are going to be that will be available to be used,” said Dorothy Rothrock, president of the California Manufacturers and Technology Association, which opposes the bill. “With simply a goal with nothing else attached to it, it’s throwing it all over to (the Air Resources Board) to do whatever they want to do.”

That board, largely made up of Brown appointees and beyond the Legislature’s control, is already at work on a Plan B—drafting rules that could act as a back-up for Brown’s environmental agenda in case SB 32 withers. But environmentalists want the state’s climate policy to have the political backing of the Legislature, knowing that it’s hard to reverse a law. If the policy is carried out simply as the go-it-alone work of a governor who will leave office in two years, it could be undone, or face a legal challenge.

And the board’s work to require emissions cuts and continue cap and trade—along with a Chamber of Commerce lawsuit asserting that cap and trade is an illegal tax—could also stymie climate policy action in the Legislature. Dean Florez, a former state lawmaker who now sits on the air board, said he’s talked to lawmakers who feel less pressure to vote for a controversial bill because the governor is pursuing his agenda without them.

“They are ‘sitting pretty’ because they can say the Governor has spoken and the courts will ultimately decide and thus there’s no hurry to act on SB 32 now,” Florez said by text message.

These Democrats “can have their cake and eat it too,” he wrote. “They get to say they are with the Governor AND with the oil companies.”

The governor himself won’t say whether he’s pulling for SB 32 or is satisfied to let the air board decide policy. All Brown’s office would say, via an email from spokeswoman Deborah Hoffman is: “We will not meet our world-leading clean air and emission reduction targets unless we solidify and redouble our commitment to the state’s cap and trade program and climate goals beyond 2020 and we will work hard to get that done.”