The first visit to the food bank is always the hardest. Michelle Venus, 52, cried. "Not while I was there," she said. "But before and after." Four years earlier, she'd been a homeowner in a $75,000 a year job. She'd donated to the food bank's fundraising drives. Now she was there to pick up food she couldn't afford to buy. "It was not what I'd expected for myself or from myself. It was just a really hard day."

Mark Weaver, 54, the former chairman of nearby Loveland chamber of commerce, tried to avoid the gaze of acquaintances he'd met when he attended the food bank's galas. "It was very humiliating," he says. "I used to take clients to their events, and all of a sudden I'm living below the poverty line." He used to earn a six-figure salary plus commission plus benefits, and also chaired the Northern Colorado Legislative Alliance, which lobbied local politicians on behalf of the business community. He made up his mind to go after a friend, a well-paid software engineer who'd also fallen on hard times, told him to: "Get over being proud."

The queue at the Larimer County food bank in Fort Collins, a town of 147,000 in northern Colorado, snakes out of the door and is mostly silent. In line there are slightly more people than trolleys. The number of families visiting here has increased more than 50% over the last five years. On average they also visit more often and need more food.

In the parking lot there are only two bumper stickers – one for Mitt Romney and one for the US navy. Inside it is set up like a grocery store. People take what they need, although there are limits for some items such as bread. From the outside, if you didn't know it was a food bank, you might think they were going to the cinema.

People often think they know what poverty looks like until they end up here, and then they realise it looks like them and many other people that they know. Weaver lives in a nice area. The first he knew that his next-door neighbour was struggling with his mortgage payments was when his house was foreclosed on and he was moving out.

The official poverty rate in the US has risen 19% since 2000 with just under one in seven Americans now poor and one in five reporting they did not have enough money to buy food last year.

But since the beginning of the financial crisis it is the 'precarity rate' that has really taken off – the number of people who feel economically precarious. Those who fear poverty, look it straight in the eye at the end of every month, face a constant battle to avoid it or slip in and out of it while struggling to retain every semblance of middle-class stability. People who may have high school diplomas, college degrees, pensions, good credit and mortgages, juggling aspiration and reality, who find themselves one lay-off or illness away from a steep and dizzying descent into hardship.

More than the half the people who use the Larimer County Food Bank are working. One in 10 have at least a college degree, almost a third have no health insurance and more than half have unpaid medical bills.

"There's been a real difference, not only in the number of people that we serve in recent years," explains Amy Pezzani, the food bank's executive director. "But also in the kind of people we serve. People think that if they're not living in poverty then they're middle class. But the official poverty level is such an unrealistic indicator of economic status. Most of the people who use the food bank are working people. These used to be referred to as 'emergency food pantries', but now it's like people are having an emergency every day. It's really just a way to exist."

'There are more people struggling that the official numbers show'

Last year the census bureau released a new measurement of poverty, which takes regional cost of living, medical payments and other expenses into account and found a third of Americans are either in poverty or desperately close to it. Half are married, almost half are suburban. "These numbers are higher than we anticipated," Trudi Renwick, the bureau's head poverty statistician, told the New York Times. "There are more people struggling than the official numbers show."

This is the fragile economic terrain on which the election is being fought: the needs and aspirations of the ever-expanding numbers of America's working poor and the far larger ranks of those anxious about joining them.

These are the people most likely to be offended by Mitt Romney's suggestion that 47% of the country see themselves as victims, who most needed the kind of change Obama promised four years ago, and have been least impressed by the apparent lack of it. These are the people at whom the ads attacking Romney's record of outsourcing and asset-stripping at Bain Capital were aimed.

They are also the ones the Tea Party sought to galvanise through their populist message against the bailout and in defence of small business. A New York Times poll in 2010 revealed that more than half of those who identified as Tea Party supporters were concerned that someone in their household would be out of a job in the next year, while more than two-thirds said the recession had been difficult or caused hardship and major life changes.

A slim majority of Americans now define getting ahead as "not falling behind". That describes life for many here in Larimer County, where between 2006 and 2010 median family income (adjusted for inflation) shrank by 9% leaving around a third of homeowners paying 30% or more of their income for housing.

The number of people using food stamps, and applying for heating assistance over the last six years has rocketed. Over the past 10 years the number of children getting free and reduced lunch doubled, while in-state tuition fees at Colorado State University, which has a huge campus in town, increased 138%.

The Fort Collins Homelessness Prevention Initiative, which provides one-time grants for emergency rent assistance, has seen a 50% increase in the number of people they are helping every year. "We mainly serve two kinds of people," explains executive director Sue Beck-Ferkiss. "One are the pay-check surfers who are used to skating by on very little. But we also see more people who are falling out of the middle class. It could be a couple who both worked on contract. The work dries up. But the world doesn't stop just because your income stops. They wipe out their savings and maybe they end up here."

'I don't think the Republican party cares about people like me'

Larimer County is a swing county in a swing state. It voted for Bush twice, but went for Obama in 2008. Now Colorado is on the fence and Mark Weaver is right there with it.

Mark is one of those rare species this election. An undecided voter with genuinely eclectic views. He's an evangelical Christian who is for gun control and a more humane immigration policy, who wants to rein in the deficit, thinks unions are dinosaurs and is against abortion although he'd rather peoples' hearts changed than legislation. He voted for John McCain last time because he didn't think Obama had the experience, and was a registered Republican until July 4 when, appropriately enough, he registered as an independent.

Both campaigns are spending millions to reach him with microtargetting on the issues they think will swing his vote their way. They're also bombarding him with ads. But all they are earning so far is his contempt. "If you took all the money they spent on the political system and elections you could feed the world," Weaver says.

He's not particularly impressed by either candidate. "Somebody's got to fix the economy, but I don't know that either of them has the guts to do it," he says. "I'm looking to vote for someone I like and trust; I've never been more distrustful of the whole thing. I wish we could vote for none of the above. I want a do-over."

Mark's fortunes began to change in the summer of 2009 when was a human resources manager in a company with 1,500 employees. He was let go and replaced by a colleague 20 years his junior on half his salary. He could have found other work elsewhere in the country, but that would have involved uprooting his three children, and he didn't think that was fair. He got another job in a start-up that involved a long commute and eventually collapsed owing him money. With his mortgage paid off and no debts, the biggest expense for a family of five was healthcare. Since everyone in the family was healthy they contemplated doing without it.

Then his youngest daughter got bitten by a rattlesnake. "That would have been a six-figure healthcare bill," he says. "If we'd gotten rid of healthcare at that point we would have been sunk." It was around that time he started going to the food bank. He stopped after he got a job at a major bookstore as a night-time accountant and head cashier paying just $9 an hour but with good health benefits, and is now getting a human resources consultancy practice off the ground.

When Pezzani heard the tape of Romney referring disparagingly to the 47% of the country who don't pay taxes she was unimpressed. "It's very difficult to see the folks that we're serving maligned in that way," she says. Beck-Ferkiss at the HPI has similar reservations. "It's hard for me to believe that Romney is focused on the population that I serve," she says.

Mark, however, says it just confirmed everything he already thought. "It doesn't surprise me about Romney because he's always struck me as a stuffed shirt. He's arrogant, and it's hard for me to get past that. It didn't change my mind about him because I always thought that about him. It was exactly the same as Obama saying "You didn't build that". Those were exactly the words I would expect to come out of his mouth."

Michelle, on the other hand, was devastated. "I was heartbroken," she says. "I was highly offended. I thought he's just disrespected me personally. I just don't think the Republican party cares about people like me." Michelle describes herself as a lifelong Democrat. She had not long moved to the Fort Collins area when her husband was diagnosed with brain cancer. They had health insurance, but with only one salary coming in they ate through their savings just to keep afloat. "We raided our personal accounts to survive."

She got a job in marketing paying $75,000 a year and remained relatively comfortable in the 2,400 sq ft house she was buying. Then she lost that job and went into consulting. "I just kept going," she says. "I lived through recessions before, and assumed I'd come out the other side." But work was drying up and when her boyfriend of six years killed himself last March she struggled to keep up. "After that I'd get up to feed my dogs but that was about it." When a client complained that she wasn't meeting deadlines she texted back: "I'm just not trying to kill myself."

Struggling to pay the mortgage on the house, which had been sold on from her bank to a loan company, she tried to renegotiate. In a conference call with an adviser and the lender, she was told that it made more sense to foreclose on her than change the terms of the loan. "I stopped paying the mortgage and got the house ready to sell," she says. She managed to sell it for a small profit and move into a place less than half the size with her son. It was around this time she found herself crying as she prepared to go to the food bank. "I just couldn't make ends meet," she says. "I don't go every week. Just when I really need something. When I first went I was worried that I would see people I knew. "

Now she's starting a new career as a journalist and has scaled down considerably and muddles through. "I have an understanding mechanic," she says. "If something happens to my car and I can't pay him everything he let's me pay what I can."

She thinks things are getting better, although she wishes they would improve faster. She blames the slow pace on the Republican congress rather than Obama. "He tried to incorporate some of what they want but ever since he got in all they've wanted to do is get him out."

The ramifications of the inability of the nation's political culture to engage with this increasingly pervasive sense of fragility goes beyond the immediate election. Since the financial crisis began five years ago, the significant shift in Americans' economic wellbeing has posed a considerable challenge to both national mythology and the political rhetoric on which it is built.

Among other things, the American dream rests on the notion of meritocracy and progress – that those who work hard will get on, that each year will better than the last and each generation better off than their parents'. Since 1977, when Gallup first asked if people thought they would be personally better off the following year, an overwhelming majority say yes every year, even though there have been four recessions. It's not a guarantee of success – indeed, quite the opposite. Inequality of wealth, and the poverty that comes with it, is tolerable on the understanding that there will be equality of opportunity. While only 2% described themselves as "rich", 31% thought it very likely or somewhat likely they would "ever be rich".

"Because differences in income in the US are believed to be related to skill and effort, and because social mobility is assumed to be high," argued Isabel Sawhill, co-director of the Centre on Children and Families at the Brookings Institution in September, "inequality seems to be more acceptable than in Europe".

But the recent downturn has delivered a severe dent to that self-image. A report earlier this year showed that between 2007 and 2010 the median American family lost a generation of wealth. Most Americans believe it unlikely that young people will have a better life than their parents – the highest on record.

'I still feel the American dream is available to me'

Meanwhile, as the National Journal's Ron Brownstein made clear recently, the sclerotic effects of class entrenchment are becoming ever more deeply embedded. In a study called 'Pathways to the middle class', Sawhill and two colleagues pointed out that nearly two-thirds of children born to parents in the bottom fifth of income stay in that category as adults, while more than three-fifths of children born into families in the top fifth remain in theirs.

But despite that it seems the belief in the American dream remains steadfast. Eighty-five percent of Americans still believe theirs is the land of opportunity, while other polls over the last four years reveal a sizeable majority of Americans still believe "the American dream is still possible and achievable for … people like you".

When Mark reflects on the last few years he falls back on his faith. "This experience has definitely made me more humble. I think God's made me more authentically who I am."

Having moved into a smaller home with her teenage son, Michelle now wonders why she surrounded herself with so many things she didn't need.

"When I was working, if I saw something I wanted I would buy it. Now I wonder if I really need it. When I see people in Target getting all these things for Halloween I think: what are you going to do with all that stuff? Where are you going to put it? I still feel the American dream is available to me. I'm not prepared to let that go yet," she says. "But I no longer think it's about being a consumer."