Arnold Schwarzenegger, George Shultz, Robert Redford, Bill Gates, James Cameron, Leonardo Di Caprio and Al Gore have all weighed in to oppose California's Proposition 23, a November ballot initiative. Now comes the uber-endorsement for the No on 23 campaign: President Obama.

"The president is opposed to Prop. 23 -- a veiled attempt by corporate polluters to block progress towards a clean energy economy," White House spokesman Adam Abrams announced Wednesday. "If passed, the initiative would stifle innovation, investment in R&D and cost jobs for the state of California."

But it is not just about the Golden State. Abrams added, "The impacts could affect us all. If successful, corporate special interests will set their sights nationwide."

The White House might well be worried: Both proponents and opponents of the measure, which would suspend the implementation of California's sweeping global warming law, say that as California goes, so go national prospects for climate change legislation.

Congress last spring killed a comprehensive bill aimed at cutting greenhouse gas emissions and spurring alternative energy, leaving California with the only economy-wide greenhouse gas law in the nation. Scientists say that carbon dioxide and other heat-trapping gases, spewed into the atmosphere by cars, trucks and industrial plants, are trapping heat in the atmosphere and disrupting the global climate.

Europe has forged ahead with strict curbs, and some U.S. states have adopted more modest laws than California's. California is set to enact rules in December aimed at slashing its carbon footprint down to 1990 levels by 2020.

Proposition 23 would suspend the regulations until unemployment in the state drops to 5.5% for a year -- a level the state has achieved only three times in the last four decades. It is backed by oil refiners that say their electricity costs and other fees would rise dramatically, as well as the California Manufacturer and Technology Assn., a Sacramento-based trade group.

-- Margot Roosevelt

Photo: Protesters march in Wilmington against Proposition 23. Texas-based Valero Energy Corp. and Tesoro Corp., the main funders of the ballot initiative, own refineries in Wilmington.

Credit: Wally Skalij /Los Angeles Times

RELATED:

TV campaign on California climate law revs up

Prop 23: Avatar's James Cameron kicks in $1 million

Meg Whitman wants to "fix" California's global warming law