As an issue in the presidential campaign, the environment is a multi-headed monster, with climate change and energy policy two of its faces. As most environmentalists will tell you, the years of the Bush administration have not been kind to their cause.

This is an administration, after all, led by former oil industry executives. Its energy policy was formed in a secret meeting convened by Vice President Dick Cheney with energy company executives. In the face of changing public opinion, it has moved from being obstructionist on efforts to curb global warming to paying lip service to its reality and the need to meet its challenges.

But actions speak louder than words. When California wanted to go beyond federal standards in limiting vehicle emissions to cut greenhouse gases, the Environmental Protection Agency refused permission (which stymied the efforts of other states, including Pennsylvania).

This decision confounded a core conservative belief that states should be free to make their own decisions, but it also underscored a defining value of this administration: When it comes to the environment, the conserve in conservative means protecting business interests first.

For the major candidates seeking their party's nomination for president, the environment is another issue that reflects an ideological divide.

• Barack Obama, now the Democratic frontrunner, is a true believer in global warming and he pledges to make combating it one of the top priorities of his administration.

On his Web site, which links energy and the environment, he cites a speech he gave in Des Moines last October in which he called climate change "one of the greatest moral challenges of our generation." He supports a market-based cap-and-trade system to reduce carbon emissions 80 percent below 1990 levels by the year 2050.

The senator from Illinois calls for investing $150 billion over 10 years in clean energy, including focusing on the next generation of biofuels and investing in low-emission coal plants. He would seek to change the cars Americans drive and the fossil fuels they burn, encouraging hybrid vehicles and raising fuel efficiency standards. He would require that 25 percent of the energy used in the United States by 2025 comes from clean, sustainable sources such as wind, solar and geothermal.

• Hillary Clinton is very much in tune with her Democratic rival. She too favors a cap-and-trade system for carbon emissions, stronger energy and auto fuel standards and a large increase in funding for green research. She would set up a $50 billion Strategic Energy Fund (to be paid for partly by oil companies) in order to make investments in alternative energy.

She too wants to reduce greenhouse gas emissions by 80 percent by 2050. She favors renewable energy generating 25 percent of electricity by 2025 and she supports a drive to reduce electricity consumption 20 percent from projected levels by 2020.

The senator from New York is not to be out-wonked on any issue, especially energy and the environment. Her list of goals seems to incorporate every conceivable idea. For example, she would require that all federal buildings designed after Jan. 20, 2009, be zero-emission buildings.

• John McCain is not the darling of conservative elements in his Republican Party -- and his attitude on global warming is one reason. He is not afraid to say that he thinks it is real.

His Web site has a section titled "Stewards of Our Nation's Rich Natural Heritage" -- itself an encouraging sign -- which lauds his "proud record of common sense stewardship" and "his commitment to clean air and water and to conserving open space."

He believes that "America's economic and environmental interests are not mutually exclusive, but rather inextricably linked. Our economic prospects depend greatly upon the sustainable use of ample and unspoiled natural resources. A clean and healthy environment is well served by a strong economy. History shows that poverty is a poor steward."

Encouraging stuff, but it is longer on noble intentions than practical details. It's an open question whether the senator from Arizona, as a self-proclaimed conservative, would crack the whip on industries when it needs to be cracked. He supports a market-based cap-and-trade system to achieve limits on greenhouse gas emissions and stands for energy efficiency in general.

• Mike Huckabee clearly isn't worried about global warming, although he does acknowledge a duty for humans to be stewards of the planet. The former governor of Arkansas sees energy independence as a global security issue. He would support oil drilling in some of America's most vulnerable places while at the same time promoting alternative energy sources.

The environment, in its attendant guises of energy policy and climate change, may not capture as many daily headlines as the war in Iraq and the withering economy. But in the long run a warming planet and a deteriorating environment threaten major trouble.

The Post-Gazette favors bold, aggressive steps to correct past follies and decades of denial. Fortunately, it seems that whoever wins in November will do better than the Bush administration in facing up to the problem.