LEAFLETS under one arm, Mark Reckless is preparing to canvass a hilly street in Rochester when a resident approaches him and thrusts an envelope into his hand. Informing the politician that it contains a declaration of support for him, he launches into a diatribe about immigration. “We are an island race,” he begins, complaining that newcomers “just don’t mix.” Some parts of this Kent commuter town south-east of London have practically become ghettos, he insists: “You drive through them with your car doors locked, know what I mean?” As Mr Reckless wends his way from one neat semi-detached house to another, the near-ubiquity of such views becomes evident. In some cases they are motivating residents to support him in the upcoming by-election. Last month he defected from the Conservative Party to the populist UK Independence Party (UKIP), praising its commitment to cutting immigration. It was the latest in a series of coups for UKIP. Douglas Carswell, another Tory defector, won the Clacton by-election on October 9th; the party is on 16% in the latest YouGov poll (up from 3% in the 2010 election); and Nigel Farage, its blokeish leader, has been offered a place in one of the televised leaders’ debates before next year’s general election. Tories believe that UKIP could cost them power, so are desperate to use the Rochester by-election on November 20th to terminate its run of wins.

David Cameron is therefore scrambling to toughen his immigration policies. In an earlier bid to curb UKIP’s rise, the prime minister promised to reform Britain’s EU membership and put the result to an in-out referendum during the next parliament. Now he claims he will make restrictions on EU immigrants’ rights a cornerstone of this negotiation. It has also been reported that he is planning a “game-changing” new policy on the issue, possibly to be unveiled before the by-election. This could involve restricting overall numbers of immigrants from elsewhere in the EU.

Fulfilling this pledge would be vexatious, to say the least. In a speech in London on October 20th José Manuel Barroso, the outgoing European Commission president, warned that Brussels would never accept an “arbitrary cap” because this would undermine freedom of movement and the equal status of EU citizens. Mr Reckless and his new party agree, citing the comments as proof that Britons must leave the EU if they want to cut immigration.

Most studies suggest that they do. Britain is economically and culturally richer as a result of its immigrants and it is relatively good at integrating them. But Britons are gloomy about their impact (see chart 1). No one simple reason for this exists: Britons’ objections are a varied tangle of the rational and the irrational, making things yet trickier for poor Mr Cameron. For example, their views do not really track the level of immigration. According to the Migration Observatory at Oxford University, collating surveys from the past decades shows that a fairly steady majority of Britons think the rate too high, whatever it actually is (see chart 2). When numbers shot up in the mid-2000s, as citizens of new EU member states moved to Britain to work, opinion barely budged.

How, then, to explain Britons’ xenoscepticism? One explanation is that immigration is a prism through which voters view their personal trials and disappointments. It does not take much door-knocking around Rochester to find evidence of this. Leaning on a walking stick, one softly-spoken, middle-aged woman tells Mr Reckless (pictured below left, with Mr Farage) that she was employed as a school cleaner before her health problems began. She wants to work but is prone to collapsing, only just getting by on disability benefits and money from her parents. Her son is struggling to find a part-time job. “They come over here,” she says gnomically, “they take out of the system but they haven’t contributed to it.” That such folk use immigration to explain their predicaments is perhaps for lack of other subjects. For most of the past three decades the economy, unemployment or the health service has been a priority for the British; now such concerns have dropped away, leaving room for immigration to rise up the agenda (see chart 3).

Of course, some of the anxiety is grounded in direct contact with immigrants. But that varies from place to place. In flat, arable Lincolnshire and Norfolk eastern European migrants working in the vegetable fields stoke claims that local workers are being undercut. There the job of politicians is evidently to improve enforcement of the minimum wage and to crack down on gangmasters. In other places strains on public services are a factor. In Rochester, for example, locals worry that immigration exacerbates problems at the nearby Medway Maritime Hospital, which has fallen far short of its targets. That Britain, unlike some of its international counterparts, has universally accessible health and welfare services rather than insurance-based ones may explain why its antipathy to immigration is greater.

Different places also respond differently to the various sorts of immigrants. In Rochester, unlike in the Fens, eastern Europeans are relatively well-liked. One local restaurateur describes the hierarchy. Most favoured are the Indians, who arrived decades ago and run curry houses on the High Street. Then come the Poles, who tend to speak good English (“they’re like us; they work in the week and go to the pub on the weekend,” opines one UKIP activist). The Kurds and Kosovars are the least popular, because they struggle with the language and are thought to overburden schools. Parts of the town are like a Little Kosovo, sighs the restaurant owner.

Despite such grumbles, though, the British Social Attitudes (BSA) survey finds that cultural concerns are secondary to economic ones. It also reveals that proximity to immigrants breeds tolerance of them. Residents of multicultural London have the most liberal views. Conversely, some of the least diverse bits of Britain are the most sceptical about immigration. In a Survation poll in August over four times as many Clactonites cited it as the issue most important to them as cited the economy, though only 4% of local residents are foreign-born (compared with 13% nationally).

Into this mix of personal experience and imagination—and the odd splash of old-fashioned bigotry—goes a hefty dose of mythology. The popular press is at least partly to blame. A study of newspaper reports over the period 2010 to 2012 by the Migration Observatory found that the word most commonly attached to “immigrant” was “illegal”. Among the other most frequently associated terms were “influx”, “sham” and “wave.” Sure enough, according to Ipsos MORI, the average voter thinks foreign-born immigrants constitute 31% of the population, well over twice the correct proportion. Such misconceptions certainly help account for Britons’ hostility. The BSA study tested respondents’ knowledge of immigration controls. Those who answered correctly were over twice as likely as others to think that the benefits of immigration outweigh the costs.

Mr Cameron cannot credibly parrot voters’ sometimes irrational views. But, rightly or wrongly, immigration is increasingly a priority for Britons. What can he and other mainstream politicians do? A prospective Tory candidate for the Rochester by-election suggested that she supported UKIP’s stance on immigration. In the opposition Labour Party (which has limited itself to talking about the importance of the English language and minimum-wage enforcement) several MPs have called for their leaders to take a harder line. But as sensible types in both parties have pointed out, it is impossible to out-UKIP Mr Farage. Better to appeal to voters’ appetite for credibility and authenticity—and to mix reassurance and myth-busting with policies to relieve strains on public services and living standards. A messy solution, it is true, but no messier than the problem itself.