So the blown-out oil well in the Gulf of Mexico has finally stopped gushing, plugged with heavy mud and awaiting the ultimate “kill” by a relief well.

Yet, even with the largest oil spill in the nation’s history in the background, what seems to have been killed much more quickly is Washington’s will to take meaningful action on the environment. After axing climate-change legislation in late July, the Senate is now taking up a modest energy bill — and even that effort may go nowhere.

Hopes for a pivotal BP-driven eco-moment — remember President Obama’s call in June for a new “national mission” to get America off fossil fuels? — have dissipated, seemingly confirming the common view that powerful energy firms, and corporate America more broadly, stand as the sworn enemies of any bold new environmental rules, and that they have the clout to get their way.

Except that old view is no longer quite right. Big business is more divided on energy and the environment than ever, and the growing rift reflects major power shifts in the economy.

On one side are business leaders and shareholders who derive their wealth from resource extraction, fossil-fuel-based power generation and energy-intensive manufacturing — the “dirty rich.”

On the other are business leaders who run knowledge or service companies that generate little pollution — the “clean rich.”

The dirty rich are dying off, and the clean rich are coming of age.

Of course, the dirty rich still have enough juice on Capitol Hill to kill bills they don’t like. ExxonMobil, for example, is not just the second-largest American corporation; it also has some of the deepest pockets for lobbying, spending $27.4 million on it in 2009, more than any other company.

But the larger transition is clear: America is witnessing the twilight of the dirty rich and the inexorable move of economic power to the clean rich.

What’s more, environmental values are spreading fast through affluent America, with more super-wealthy individuals putting their money behind green causes and more upscale voters expecting government action to protect the planet.

Climate legislation may be dead for now, but if big money really talks in America, the long-term prospects for tougher environmental rules seem quite good.

It is hard to understate how dramatically the sources of business wealth have shifted in the past half-century. Of the top 20 companies on the Fortune 500 list in 1960, 16 were engaged in heavy industry, such as U.S. Steel and DuPont, or resource extraction, such as Texaco and Mobil. This year’s list includes six such companies in the top 20.

Meanwhile, the dirty rich are fading from the Forbes 400 list of the wealthiest individuals. When the list was first published in 1982, 38 percent of its members had made their fortunes in oil and manufacturing, and 12 percent were in finance and technology.

2006, those ratios had nearly flipped: 36 percent of the richest Americans made their wealth from finance and tech, while 17 percent earned it from manufacturing and oil.

The dirty-rich billionaires on the Forbes list are mostly older — such as industrialists David and Charles Koch, both in their 70s. Among recent newcomers to the list, few have been from dirty industries. More typical is Facebook founder Mark Zuckerberg, who made the list in 2008 at age 24.

Even Texas doesn’t have as many dirty rich as it used to. Fewer than half of the state’s billionaires made their money in oil or energy. The two wealthiest Texans today are Alice Walton, an heir to the Walmart fortune, and Michael Dell, a computer entrepreneur.

The same pattern holds elsewhere. The great fortunes of Colorado used to be made from oil or mining, and the state’s politicians were often creatures of those industries, and unfriendly to environmentalists. Now, the state’s super-rich include satellite TV mogul Charles Ergen and Quark founder Tim Gill.

In the early 1980s, the only Forbes 400 member from the Pacific Northwest was a timber baron. Today, a half-dozen billionaires live in the region, and most made their money in technology.

POLITICIANS GET NEW DONORS

This seismic shift in who gets rich is fast changing where politicians get their money and to whom they listen. A torrent of new cash has flowed into politics from the finance, tech and entertainment industries, and especially from the legal profession, which gave twice as much to national candidates in 2008 as any other sector.

Dirty industries that once wielded enormous clout on Capitol Hill — autos, steel and mining — aren’t the players they once were. Political contributions from the entire coal industry amounted to $3.5 million in 2008, while Microsoft employees contributed $3.3 million.

In 2008, John McCain far outraised Obama among employees of energy and natural resources companies, pulling in $4 million. Not bad, except that Obama bested McCain in the communications and electronics sector 5-to-1, raising $25.5 million. Until the 2002 election, the oil and gas industry was consistently among the top 10 sources of money for federal candidates, according to the Center for Responsive Politics. In 2008, it ranked 16th.

The picture looks quite different when it comes to money for lobbying, with dirty industries still among the biggest spenders in Washington.

But the winds may be shifting: The once-feared automotive industry is now so weak that Detroit could barely swing a bailout last year and watched helplessly in late 2008 as its greatest champion in Congress, Rep. John Dingell, D-Mich., was ousted from a powerful chairmanship by Rep. Henry Waxman, D-Calif., a strong environmentalist.

Of course, new-economy giants such as Hewlett-Packard have faced withering criticism of their environmental records, and the pollution from high-tech products can certainly be serious. The difference is scale.

Other knowledge industries, such as the legal profession, are about monetizing cognitive skills and have little to do with the old-economy model of converting natural resources into wealth. So some of the fastest-growing and richest parts of the economy aren’t much affected by environmental laws, which is why a growing slice of America’s business elite has little incentive to battle them.

An ever-larger contingent of clean-tech entrepreneurs and investors will score big if Congress acts to push up the price of carbon. Last year, George Soros pledged to make $1 billion in renewable-energy investments. Other billionaires, including Warren Buffett, Bill Gates, John Doerr and Vinod Khosla, are placing major bets in that sector.

Apart from self-interest, many of the clean rich care about the environment. They tend to be highly educated, and quite a few have scientific training. They understand that climate change is real and must be addressed now.

Google, which is run by three computer scientists, set out to be carbon-neutral several years ago and says it has achieved that goal. Intel co-founder Gordon Moore, a chemist by training, is giving hundreds of millions of dollars to help preserve fragile ecosystems.

WEALTH, ENVIRONMENTALISM LINKED

But the roots of the clean rich go deeper. The modern environmental movement emerged in the 1960s, fueled in large part by the spread of affluence and education. There is a logic to that link: Once your material needs are met, you can turn your attention to other concerns, whether saving polar bears or the Amazon.

It is hardly news that affluent liberals often fret more about the environment than working-class voters. But the class divide is poised to have a larger political impact.

One reason the Republican Party can blithely block attempts to address climate change, one of the gravest threats facing humanity, is that its political base is heavily weighted with less-educated and less-affluent voters who live in rural areas and small towns — and who aren’t keen on government activism to protect the planet. A poll last year by the Pew Research Center for the People and the Press, for instance, found that support for legislation to limit carbon emissions was 16 points higher among college graduates than those with a high school diploma or less.

If the GOP is to build a durable majority, it will have to move beyond that constituency. Even if Republicans take control of the House this fall, that won’t change the fact that the Palin and Limbaugh wing has badly hurt GOP fortunes by alienating affluent and educated donors and voters.

Wooing back such natural allies, especially the clean rich, will require tacking to the center. And climate change, an issue driven by scientific evidence and with appeal in this newly influential community, is a great candidate for a softened stance.

Its time will come soon — and could come even faster if a few farsighted Republicans recognize their plight and decide to hasten that transformation.