WASHINGTON — After eight years with a Texas oil man as president, environmentalists are looking forward to a greener White House.

Whoever wins November's presidential election, environmentalists agree, is bound to be better than President Bush has been on their concerns. He has been dubbed by the League of Conservation Voters as "arguably the most anti-environmental president in our nation's history" for supporting efforts to weaken clean air and water laws and drill for oil in the Arctic National Wildlife Refuge.

Unlike Bush, presumptive Republican nominee John McCain has been a leader in efforts to fight global warming, sponsoring 2003 legislation to reduce carbon dioxide emissions at a time when many in his party were still doubting the existence of climate change. The Arizona senator was by far the most pro-environment Republican to seek his party's nomination for president this election cycle, environmental groups say.

On the Democratic side, New York Sen. Hillary Rodham Clinton has used her position on the Senate environment committee to push for tougher clean air, water and toxic waste laws and stronger protections for children's health. Illinois Sen. Barack Obama, whose oldest daughter, Malia, suffers from asthma attacks made worse by air pollution, also is viewed as a passionate environmental advocate.

"This is the first time in many years that we will have two general election presidential candidates who will be good on the environment," said Jim DiPeso, policy director of the moderate Republicans for Environmental Protection.

One of the most dramatic changes in environmental policy is expected to happen on global warming. All three candidates support laws to force deep reductions in greenhouse gas emissions that cause global warming. Bush, despite setting some voluntary goals this month to slow climate change, opposes mandatory limits on carbon emissions because he says they would raise energy costs and put U.S. businesses at a disadvantage against India and China.

"I think the great news is that we can actually expect something to happen when a new president takes office in January," said Cathy Duvall, political director of the Sierra Club. "Whoever is sitting in the White House after the election will finally take up and address global warming."

REDUCED EMISSIONS

Clinton and Obama both support an 80 percent reduction in carbon emissions by 2050. McCain has sponsored legislation that would reduce those emissions 65 percent by the same date.

Bush, in a speech last week, set a much more modest goal of freezing the growth of emissions by 2025 before starting to reduce them.

"When compared to the current administration, the differences that McCain, Obama and Clinton have with one another are relatively small," said Robert Stavins, an environmental economist at Harvard University.

Still, most environmental groups are clearly hoping for a Democratic victory in November. Obama and Clinton, they say, are willing to go further and faster than McCain to stop global warming and have been more consistent in voting with the environmental community over the years. McCain, for example, has voted against renewable energy standards that supporters say could reduce U.S. dependence on foreign oil as well as pollution.

Clinton has earned the League of Conservation Voters highest "lifetime score" with an 87 percent out of a possible 100 percent on her overall legislative record. Obama is close behind her with a lifetime score of 86 percent. McCain's lifetime score is 24 percent, low compared with the Democrats but far above the average for Republican congressional leaders.

"To his credit, Senator McCain has made global warming a priority, but his specific plan falls short of what science says we need to do," said Gene Karpinski, president of the League of Conservation Voters. "The Democrats' plans are far superior in terms of getting the job done."

GOP SUPPORT NEEDED

But pro-environment Republicans say McCain may have the advantage over the Democrats when it comes to persuading Congress to pass comprehensive legislation to reduce global warming. Although Democrats are expected to retain control of Congress after the November election, the Senate still might be shy of the 60-vote majority it needs to prevent conservatives from using a filibuster to kill global warming bills.

"It took a Republican like Richard Nixon to go to China, and a Republican president will be able to accomplish certain things on climate policy that maybe a Democrat couldn't do," DiPeso said.

Whoever does it, it won't be cheap or easy to push America off of its reliance on fossil fuels and onto cleaner, renewable sources of energy, Stavins said.

The solution the Senate is scheduled to take up this June is the creation of a cap-and-trade system in which a power plant or factory that released more greenhouse gases than permitted by law would have to buy allowances for the extra emissions. The allowances would be sold by companies that cut their emissions below the required cap.

Over time, the cap would get tighter and tighter so all companies would have to come up with ways to meet the emissions requirements and could not buy their way out of them forever.

Bush has made it clear he will not sign the bill if it passes Congress. But congressional leaders say their efforts will outlast him.

"From all the evidence we have now, if Congress passes that kind of bill next year, all three presidential candidates would sign it," Stavins said.