Richard Daley hoped he would spend more time at his Kentucky vacation home in retirement. Instead, the 60-year-old former engineer, has cut his number of visits by half because of the soaring cost of driving the 200 miles from his home in West Chester, Ohio. "On a fixed income, we just can't keep absorbing these increases," he says.

Mr Daley is one of millions of Americans rethinking their approach to energy consumption as petrol prices hit record levels.

According to the Department of Transportation, US drivers travelled 30bn fewer miles between November and April, compared with a year earlier, the biggest drop since the 1979 energy crisis.

While Mr Daley's story is increasingly familiar, his carries added weight because he lives in one of the most important battleground states in November's presidential election.

His heavily Republican county on the edge of Cincinnati helped deliver George W. Bush's narrow victory in Ohio four years ago and John McCain needs to win by a big margin there if he is to hold the state.

Describing himself as an undecided independent, Mr Daley supports Mr McCain's plan to lift the ban on fresh offshore oil and gas drilling around the US coast. But he also favours Barack Obama's proposal to levy a windfall profit tax on oil companies and invest the proceeds in renewable fuels: "We need to exploit all the oil we have, but, in the long term, we have to find alternatives," says Mr Daley. Energy has soared towards the top of the election agenda as petrol prices have topped $4 a gallon for the first time.

Three in four voters say the issue will be "very important" in determining their vote - outranking taxes, terrorism and the Iraq war - according to a recent poll by the Pew Research Centre. Asked who they trusted most to handle the energy issue, respondents favoured Mr Obama over Mr McCain by 18 percentage points. "Voters are making the simple conclusion that if you change the party in the White House somehow things will get better," says Larry Sabato, a political scientist at the University of Virginia.

Mr McCain is hoping that public opinion will swing in his favour as attention focuses on the debate over offshore drilling. The Arizona senator last week called for an end to the 27-year moratorium on oil exploration in US waters, setting him apart from Mr Obama, who supports the ban. Polls show that two-thirds of Americans favour his new position.

For Stephan Jones, a self-described independent conservative from Gratis in rural western Ohio, the drilling pledge has helped cement his support for Mr McCain. "I realise it's going to take 10 years for the oil to start flowing but if we'd started 10 years ago we wouldn't be in this mess," he says. Now retired, Mr Jones spent most of his working life at a General Motors plant in nearby Dayton. It was announced this month that the factory, which makes gas-guzzling sports utility vehicles, would close in 2010 because of the stampede towards more fuel-efficient models. Mr Jones's daughter is among the 2,500 people expecting to be laid off. The GM decision has deepened the economic gloom hanging over Ohio, which has lost more than 200,000 jobs over the last seven years - its sharpest rate of decline since the Great Depression.

Herb Asher, a political scientist at Ohio State University, says high energy prices are feeding into broader concern about the economy. "Voters are worrying about how much it costs to get to work and whether they will have a job when they get there," he says.

Mr Obama lost the Ohio Democratic primary to Hillary Clinton but a recent poll put him six points ahead of Mr McCain, easing doubts about his ability to win the heavily white, working-class state.

Jeanie Pelfry, a 52-year-old care worker from Clark County, is among those who voted for Mrs Clinton but she plans to support Mr Obama in November. She agrees with Mr McCain on offshore drilling but that alone will not win him her vote. "McCain would be just as bad as Bush," she says. "My father-in-law remembers the Great Depression and he thinks we're headed for another."

For Julie Lane, a 59-year-old unemployed woman from Cincinnati, rising energy and food prices have combined to push her household budget to breaking point. She has stopped buying meat, except for discount burgers, and tries to make a tank of petrol last a month.

Mr Obama hopes a large turnout of African-Americans will help him carry the Cincinnati area, where Mr Bush narrowly beat John Kerry, the Democratic challenger, in 2004. But Ms Lane will not be among them. "I'm not voting for anyone," she says. "It doesn't make any difference who wins. They're all in with the oil companies."