A campaign to make Washington the second state in the country to cut greenhouse gases coming from cars took a major step forward yesterday when the state Senate approved a bill adopting many of California's tougher limits on tailpipe emissions.

The 29-19 vote marked a major victory for environmentalists and a defeat for carmakers and car dealers, who are trying to beat back the spread of regulations. Yesterday's vote, however, doesn't mark a total victory for proponents. They had to water down some provisions to win key votes from rural Democrats, and some of the changes could leave the legislation vulnerable to legal challenge if it becomes law. Backers of the Senate bill must also work out differences with a stricter version that earlier passed the House 53-42.

Still, supporters were elated over passage of legislation they said would ensure Washington's air improves and force the auto industry to build more fuel-efficient cars. Proponents hope it means consumers would find a broader selection of cleaner vehicles.

"This is probably the biggest environmental vote we've taken on the Senate floor in 10 years," said Sen. Erik Poulsen, D-Seattle, who helped shepherd the bill through the Senate.

Opponents, meanwhile, warned the legislation could leave Washington at the mercy of whatever rules were created in California. With Washington air already meeting federal air-quality standards, they questioned the need for regulations that could raise the cost of a new vehicle, drive vehicle shoppers to other states or reduce the availability of popular SUVs and trucks.

"This is the Kyoto treaty come to Washington state," warned Sen. Val Stevens, R-Arlington, referring to the international treaty to cut greenhouse gases, which the U.S. has not joined. "This is an attempt to turn Washington state into another California."

The legislation would impose tighter restrictions on emissions of toxic and smog-causing chemicals from new cars and would force fuel-efficiency improvements to shrink greenhouse-gas emissions from new cars sold in Washington state, starting in 2009. Scientists warn a buildup of greenhouse gases in the atmosphere, such as carbon dioxide, could raise global temperatures.

But senators removed a major piece of the California regulations. That provision required carmakers to meet quotas for selling a certain number of super-clean-running vehicles each year. It drew objections from Washington auto dealers worried it could force them to sell less-popular cars.

That change, along with several others, was aimed at answering the concerns of rural Democrats like Sen. Mark Doumit, D-Cathlamet, who had wavered about supporting the bill. Doumit, who represents the southwestern corner of Washington near Oregon, said without those amendments, he wouldn't have been able to vote yes, given the concerns he heard from local car dealers.

In addition to canceling the sales quotas, the Senate legislation would require Oregon to adopt similar regulations before Washington's could take effect. If Oregon adopts the regulations, the rules would apply to new cars sold in Washington starting in 2009.

Seven New England states already use California's limits on toxic and smog-causing emissions. But they haven't adopted California's greenhouse-gas restrictions, which require a 30 percent cut in such emissions from new cars by 2016. The auto industry has filed a lawsuit challenging the California greenhouse-gas rules.

Getting rid of the clean-car quotas would result in less improvement in toxic or smog-causing emissions in Washington. Supporters acknowledged it also could leave the legislation vulnerable to legal challenge, because federal law bars states from creating their own auto-emissions rules. States can opt to follow either the California rules or the federal rules. But getting rid of the car quotas would make Washington's rules different from California's.

Poulsen said the compromise was needed to ensure the legislation's passage.

"That amendment kept this bill alive to see another day," he said.

Early yesterday it appeared questionable whether the bill would survive a Senate vote. Senators described the likely vote as very close before debate began. Gov. Christine Gregoire arrived to lobby several Democratic senators, including Doumit, to vote for the legislation. Most amendments passed on a nearly party-line vote.

However, in the final vote, several suburban Republicans sided with Democrats to support the bill, including Senate Minority Leader Bill Finkbeiner of Kirkland, Sen. Republican floor leader Luke Esser of Bellevue and Sen. Dave Schmidt of Mill Creek. Tim Sheldon, D-Potlatch, was the only Democrat to vote against it.

Schmidt had expressed reservations about the bill earlier in the day. He said both sides were exaggerating what the bill would do. Environmentalists overplayed the benefits of the bill, particularly in a region where air quality meets federal standards, he said. After the vote, he said opponents were exaggerating how much car prices would rise. And, he said, he had heard strong support from constituents.

"The e-mail and letters coming in were overwhelmingly supporting it," he said.

The bill was a top priority of environmentalists this year. They argued the bill could produce health benefits for Washington residents and save Washington drivers money by forcing automakers to sell more efficient cars. The $1,000 increase in car prices predicted by California regulators would be more than offset by gas savings, they said.

Environmentalists were jubilant after the vote, despite the changes to the bill.

"We're just very, very pleased that this bill is moving forward," said Clifford Traisman, a lobbyist for the Washington Conservation Voters and the Washington Environmental Council.

But automakers vowed to continue fighting the legislation and ask Gregoire to veto the bill if it reached her desk. They have warned it could drive up car prices by $3,000.

"We think it will be detrimental," said Eloy Garcia, director of California state affairs for the Alliance of Automobile Manufacturers. "Detrimental in terms of the vehicles that are going to be available to Washington consumers and the cost that those vehicles will be available at."

Seattle Times staff reporter Ralph Thomas contributed to this report.

Warren Cornwall: 206-464-2311 or wcornwall@seattletimes.com