"What if some poor guy in Watts retires and says, 'I want an SUV,' " Dymally said. "Do you punish him for that?"
The bill exempts low-income buyers -- defined as those at or below twice the federal poverty level -- as well as businesses with fewer than 25 workers, from surcharges.
And even for those without exemptions, "there would be a tremendous amount of choice in each category," Ruskin said, noting that cleaner SUVs, pickups and minivans would qualify for rebates.
Advocates counter that air pollution aggravated by global warming disproportionately affects poor neighborhoods. A cleaner fleet, they say, would reduce the asthma, heart disease and other illnesses that plague poor communities.
So far, 83 organizations, nearly twice as many as last year, have endorsed Ruskin's bill, including the American Lung Assn. and the Silicon Valley Leadership Group, a business coalition. But the opposition has powerful allies too, including the California Chamber of Commerce.
Gov. Arnold Schwarzenegger, a Hummer driver, has yet to take a position.
Regardless of whether the feebate bill passes, pressure is mounting to find new ways to deal with transportation emissions.
In a letter last month, Senate President Pro Tem Don Perata (D-Oakland) urged the air board to move beyond the battle with the federal government over tailpipe standards and "to act with appropriate speed and creativity" on such measures as "efficient car purchase incentives, smart growth investments, increased transit usage and other means."
Some environmentalists want the board to use its "zero-emission vehicle" regulations to require auto companies to move to a 100% hybrid-electric fleet by the end of the next decade. Others want to bring automakers under a statewide cap on emissions so that they would have to seek offsets in order to sell vehicles that emit more than a certain level of greenhouse gases.
State Atty. Gen. Jerry Brown, the Legislature and the air board are all grappling with how to encourage cities and counties to control sprawl and promote mass transit as a way to reduce driving.
State officials are optimistic that they will win their court fight against the federal Environmental Protection Agency over tailpipe standards and make a big dent in auto emissions through regulations that 16 other states have pledged to adopt. But they intend to forge ahead with other strategies in the meantime.
"Everything is on the table," Sperling said.
