Roadworks slow progress along the strip in Las Vegas. In the distance, poking between the mock Eiffel Tower and the mock pyramid at Luxor, cranes stand out against the autumn sky, building the next phase of America's seemingly permanent boom town.

But 95 miles north-east of this city, the powerhouse of Nevada with 36 million visitors a year, lies another construction site.

Yucca Mountain, projected to cost around $60bn (£32.8bn), has been chosen by the Bush administration to be the nation's nuclear waste repository, set to hold the existing 40,000 tons of waste produced to date by the country's nuclear power stations.

"This material is the deadliest substance known to mankind," said Peggy Maze Johnson, executive director of Citizen Alert, a local group that has campaigned against the repository. "It's one million times more radioactive when it comes out of the reactor core than when it went in."

In February 2002, just over a year after taking office, President Bush recommended the Yucca Mountain site to Congress. But many voters remembered that, as a candidate in September 2000, Mr Bush promised not to approve the site until it had been "deemed scientifically safe", a formulation that is credited with helping him win the state.

Four years on, and with the project stalled by legal challenges to its scientific justification, those words may come back to haunt the president in what has become a swing state. A recent poll showed that Yucca Mountain was the top issue for 3% of registered voters. "Given what's going on in this country, 3% is huge," said Ms Maze Johnson.

The polls in Nevada have ranged between a 10% lead for Mr Bush to a 1% lead for Mr Kerry. In 2000 Mr Bush won the state by 3.5%, or 22,000 votes, but Nevada has changed since then. The fastest-growing state in the US in 2003, its population has risen by 300,000 in the past four years to reach 2.4 million. For this election, there will be 1.1 million registered voters, 66,000 of them Hispanics, who traditionally lean toward the Democratic party. The increase in population means that Nevada now contributes five votes to the electoral college, one more than in 2000. Accordingly, the state has become an increasingly important and hard-fought battleground in this year's electoral race.

"In 2000 there was no campaign here; the Democrats conceded," said David Damore, assistant professor of political science at the University of Nevada at Las Vegas. "But this year there's been a strong effort to get new voters registered. The electorate looks very different to the way it did four years ago."

While voters in the state are likely to be swayed by the same big issues as the rest of the country - the economy, the war in Iraq - Nevada is one swing state where the debate about the environment, thanks to Yucca Mountain, is being aired.

John Kerry has been swift to side with opponents of the plan. In an article published in the Las Vegas Review-Journal in May, Mr Kerry accused Bush of "placing the profits of the nuclear power industry above the safety of Nevada families ... I voted against the plan to dispose of waste at Yucca Mountain," he wrote, "and as president I will fight against it."

Republicans chose to use the Yucca Mountain issue as an opportunity to depict Mr Kerry as a "flip-flopper", pointing out that he had voted in favor of a 1987 bill, nicknamed the Screw Nevada bill, which authorized consideration of Yucca Mountain as the nation's repository for nuclear waste.

In August Mr Kerry defended his position, saying: "Back in 1987 the idea of a national repository seemed like a reasonable thing ... [but] the more I have looked at the issue, the more I have learned about it, the less safe, the less comfortable I am with the possibility."

Also in August, Mr Bush told a rally in Las Vegas: "I said I would make a decision based upon [sound] science, not politics ... and that's exactly what I did."

Ms Maze Johnson said: "The president called it sound science. I call it botched science. We're not partisan, but Kerry has been with us when we've needed his vote, which isn't easy for someone from the northeast"

The northeast of the US is home to the bulk of the country's nuclear energy industry. At present nuclear waste is stored on site: across the US, 161 million people live within 75 miles of temporarily stored nuclear waste.

Local residents and politicians are keen to see it moved as far away as possible, and the sparsely-populated deserts of Nevada seemed as good an idea as any. Those opposed to the repository are also concerned about the transport of waste. It is, critics say, a disaster waiting to happen, mobile Chernobyls offering the perfect terrorist target.

"We are a one-industry state," said Ms Johnson, referring to Nevada's dependence on tourism. "If something stopped people coming, what would that do to the economy?"

At the Yucca Mountain Information Center, videos and wallcharts trumpet the efforts to ensure that the site is safe.

No mention is made of the native American name for the mountain, Moving Hill, nor scientists' nickname for it, Old Leaky. Nor is there space for a Geological Society of America report which warned that should moisture enter the mountain where nuclear waste is stored in bundles of rods, "radioactive volcanoes could form on the surface".

© Copyright Guardian Newspapers Limited 2004

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