San Diego, California - Republican presidential candidate John McCain has long touted his green credentials. But in the race for the White House this year, it doesn't look as though he will be earning many green votes.

Perhaps it has something to do with the enthusiasm whipped up by his running mate Sarah Palin, who never seems happier than when she's out in front of a crowd of enthusiastic Republicans, leading them in the party's latest battle cry: "Drill Baby Drill."

That's a reference to plans to increase US oil drilling in environmentally sensitive areas. The initial proposal is to lift the ban on drilling off the US coast, but Palin, the Alaska governor, is also known to favour drilling in the pristine Alaskan National Wildlife Reserve. She further throws McCain's green credentials into doubt with her questioning of the scientific evidence that climate change is human-caused.

Yet even prior to the meteoric rise of the upstart Alaskan politician, many environmentalists were accusing McCain of "greenwashing" - pushing pseudo-environmentalist policies purely for political purposes. They urged those who care about energy and the environment to cast their votes for Democratic candidate Barack Obama.

"The high price of oil, the country's entanglement in the Middle East, and the focus on global warming has brought green issues to the centre of the political map," said Greg Valliere, chief political strategist at the Stanford Financial Group.

Voters who narrowly focus on the high cost of petrol may go with McCain, who touts new drilling, nuclear power plants and a variety of renewable energy sources. But even this appeal may be blunted now that prices at the pump have been falling fast in the weeks prior to the election.

But when it comes to voters whose concerns about energy fall into a wider environmental worldview, the advantage certainly goes to Obama.

One reason is that such concerns have traditionally been pushed by Democrats - most notably former vice president Al Gore. But advocacy groups claim there is a huge gap between McCain's lip service to the environment and his actions.

The Sierra Club, the largest environmental group in the country, issued a pamphlet endorsing Obama, noting that McCain supports tax breaks for oil companies, has opposed tougher fuel standards, voted against investments in renewable energy and has failed to come up with an effective plan to curb global warming.

McCain is also widely blasted for his plan to build 45 nuclear power stations by 2030, dismissing those concerned about the dangers of radioactive waste as "extreme environmentalists."

"Instead of a real plan for energy independence, McCain wants to run the economy like a game show with gimmicks," said Cathy Duvall, Sierra Club's national political director. "Unfortunately, his rhetoric bears almost no resemblance to his long record of saying thanks, but no thanks to clean energy."

In contrast, Obama touts a windfall profits tax on oil companies, 150 billion dollars for investment in green energy development, a comprehensive plan to cut global warming emissions by 80 per cent by 2050 and a doubling of fuel economy standards. McCain supports a 60- per-cent cut by 2050.

Not surprisingly those policies were hugely popular among those attending the country's largest green conference, Solar Power 2008, just two weeks before the election in sunny San Diego, California.

"If Obama wins, just watch the whole green economy explode," said Greg Gahagon, a salesman of solar hot water systems.

Yet McCain would mark a sharp departure from the environmental traditions of his own Republican Party. The Arizona senator supports cap-and-trade legislation that would place limits on the greenhouse- gas emissions of US companies, something long opposed by President George W Bush.

Douglas Holtz-Eakin, McCain's chief economic advisor, last week said energy and climate change would be the two top legislative priorities of a McCain administration.

Both Obama and McCain have also stressed the job-creating potential of the renewable energy sector, which is clearly set to get a boost no matter which candidate makes it into the White House.

"Renewable power is in some ways independent of the candidates," said John Gazal, a representative for a major solar power company at the San Diego conference. "No matter who is elected this country has to change its energy policy. "But whose heart is in it? And who will do a better job? Ninety-nine per cent of people here will tell you it's Barack Obama."