Commuters on the A414 highway in Essex, England, have recently become used to a curious sight. Every day between 7 and 9 a.m., then again from 4 to 7 p.m., a man in a peaked cap perches on a small chair by the divided highway, beams at the oncoming traffic and gives drivers the thumbs-up sign.

"You have to look them in the eyes," explains Robert Halfon, the Conservative member of Parliament for Harlow in Essex. Many of the drivers return the thumbs-up gesture and honk their horns. "Halfon, yeah!" shouts one man, leaning out of the window of his van as it speeds past.

Halfon is no ordinary MP. He has won admirers from across the political spectrum by fighting a series of campaigns on consumer issues, from taxes on bingo halls to surcharges on electricity bills. He is best known for persuading the Tory-Liberal Democrat coalition government to cancel every planned fuel-duty increase since 2010.

The MP calls his brand of politics "white-van Conservatism" — a reference to the aspirational working-class voters who make towns like Harlow, northeast of London, such crucial bellwethers. They voted for Margaret Thatcher in the 1980s and Tony Blair in the 1990s. But this time they are proving especially hard to woo.

The Tories can point to a rebounding economy and an increasingly popular leader in David Cameron. But with just a few days before the general election on May 7, they are tied with the opposition Labour Party, as they have been throughout the campaign.

In order to form another coalition with the Lib Dems, the Tories must hold almost all of their seats in the House of Commons. Oddly, the greatest challenge to their continued rule does not come directly from Labour: Over the course of this Parliament few voters have moved from the Conservative camp to the Labour one, or vice versa. The Tories' real problem is the populist UK Independence Party (UKIP) and its strong appeal to white-van man.

More than one in 10 people who voted Conservative in 2010 have since left the party for UKIP, which detests the European Union and immigration. The defectors are typically male, white and working-class. Lynton Crosby, the Tories' campaign chief, reckons that the party's typical target voter earns about $23,000 a year — 40 percent less than the national average — reads the Sun on Sunday, a right-wing tabloid, and values economic and national security above all else.

This analysis colors the entire Conservative campaign. In an interview on April 6, Cameron urged UKIP voters to "come home." At the party's manifesto launch on April 14, he described the Tories as "the real party of working people." Two weeks later he called it the party of "the grafters and the roofers and the retailers and the plumbers." He talks endlessly about security.

The Tories have courted white-van man in their manifesto and in the promises they have made on the campaign trail. The prime minister has pledged to create 50,000 new apprenticeships, expand free child care and take those earning the minimum wage out of income tax. He even promises to legislate against any increases in the government's main revenue-raising taxes until 2020. He has revived Margaret Thatcher's totemic bid for working-class support by promising to extend the "right to buy" social housing to tenants of housing associations.

The pursuit of van-driving voters also partly accounts for the Conservatives' frequent warnings about the risk to Britain's economic and political stability of a Labour government propped up by the separatist, left-wing Scottish National Party. Polls suggest UKIP supporters worry more about this than most.

Halfon reports that voters are now raising the issue on the doorsteps. He declares himself delighted at his party's campaign; after the election, he plans to frame the newspaper coverage of its manifesto. On April 30 the Sun newspaper endorsed the Tories. Yet the Tories' white-van-man strategy is not yet working well enough. The party has not achieved the long-expected "crossover" with Labour in the polls mainly because it has not squeezed UKIP enough.

The best explanation is that many voters still doubt that the Conservatives understand their lives and interests. Cameron takes no pains to hide his poshness. And at times the party has helped to reinforce this sense: from its chief whip swearing at a policeman (allegedly calling him a "pleb") to the economically savvy but politically masochistic decision to cut income tax on the highest earners in the "omnishambles" 2012 budget.

More damagingly, low-income voters are not feeling better off than they did in 2010. Though unemployment has fallen steeply, this is partly the flip side of insecure work and stagnant wages. Tories protest, with reason, that low wages are better than none at all — and that at least things are not going backward. But the van drivers can be forgiven for not being overwhelmed with gratitude to the governing party. As Halfon's roadside vigil demonstrates, it can take extraordinary efforts to persuade such voters that Conservative MPs are truly on their side.

Copyright 2013 The Economist Newspaper Limited, London. All Rights Reserved. Reprinted with permission.