Before entering the California Assembly last year, Fran Pavley taught civics at a junior high school. That experience left her ill prepared, though, for the political realities she encountered during the year and a half she spent pushing a landmark greenhouse-gas regulation bill through the legislature. Car makers and oil companies spent an estimated $5 million attempting to sink it, and she herself was ardently attacked by talk-radio hosts for impinging on the freedom of Californians to drive SUVs and other large vehicles.

Pavley's bill became law in July, surprising not only its opponents but many of its supporters. The legislation requires that by 2005 the state air-quality board come up with specific regulations to limit greenhouse-gas emissions from automobile and light-truck tailpipes.

As the only state allowed to set air pollution controls stricter than those mandated by federal law, California is an almost constant environmental battlefield. And in contrast to other states, vehicles produce most of its greenhouse gases. There was strong pressure from environmental forces to move on the issue last year, with both the legislature and governor's mansion in Democratic hands for the first time in two decades. Still, many legislators were worried about taking on such a large task. Given the lobbying strength of the opposition, they saw it as a certain failure, and felt its defeat would kill momentum toward tougher fuel standards at the federal level.

And Pavley, 53, a former suburban L.A. mayor who had been in the legislature only a few months, was too new to be an ideal sponsor. She had one important qualification, however: She was willing to take on the fight when more prominent legislators were avoiding it. "We were happy at that point to find any progressive author, because we knew it would be a difficult bill," says Russell Long, of the San Francisco- based BlueWater Network, the group that initially drafted the greenhouse bill.

The consensus around the Assembly was that the bill would die in committee. But Pavley proved to be diligent and capable, attending planning meetings usually relegated to staff and chasing down colleagues individually to ask for courtesy votes. State Representative Marco Firebaugh told Long, "This is a bad bill. I've voting for it because Pavley asked me to."

The legislation survived and was ready to reach the floor in June of last year, but Pavley held off on a vote until this past January so she could broaden her backing. She distributed polls demonstrating overwhelming popular support for the bill, even among SUV owners. She also got help from water-quality districts, religious leaders, tech executives from Silicon Valley and celebrities such as Paul Newman, Tom Hanks and Bill Clinton, who called wavering members. The most important support Pavley received, however, came from the legislative leadership.

Herb Wesson, her Assembly seatmate, became Speaker two weeks before the floor vote and used the bill as a means of establishing his power. When one Democrat missed the vote, Wesson took away his committee chairmanship. The bill passed the Senate easily but looked like it might die a procedural death on its way back to the Assembly. Senate President Pro Tem Tom Burton then inserted its text into an unrelated bill, making final passage easier. That was a move Pavley hadn't covered in her civics class. "All the years I taught how a bill becomes law," she says, "we didn't talk about that possibility."

Already legislators in several states are hoping to require their environmental departments to follow California's new tailpipe- emissions standards once they are released. And in the Assembly, colleagues are wondering what Pavley herself will do for an encore. "A few people have said after carrying that bill, people are going to be descending on my office wanting me to carry all the difficult bills over the next few years," Pavley says. "My staff says they think we should focus on puppies and children."