ON OCTOBER 8th Nigel Farage predicted that victory for his UK Independence Party (UKIP) in both of the next day’s by-elections would be a political Krakatoa. The eruption was only narrowly averted. Douglas Carswell, who had resigned as Conservative MP for Clacton to contest the seat for UKIP, became the party’s first elected MP. But in Heywood and Middleton, near Manchester, Mr Farage’s insurgency fell 618 votes short of replacing the former Labour MP, who had died in office—a stonking achievement, all the same.

Westminster and Fleet Street are gripped by UKIP’s rapid rise. Another Tory defector, Mark Reckless, may win a by-election in Kent on November 20th. The two main parties are panicking. Mr Farage’s nationalist lot appears to be winning over disaffected, ageing voters from both (though primarily the Tories), especially in backwaters like Clacton. In response, David Cameron has promised Britons a vote on leaving the EU and has dangled goodies—most recently, an inheritance tax cut—before older voters. On October 14th Ed Balls, the Labour shadow chancellor of the exchequer, called for curbs on immigrants’ access to benefits.

But homogeneous, greying Clacton is not Britain. According to a YouGov poll only 11% of voters say they will probably vote for UKIP in next year’s general election. Even including those who say they would consider doing so, this rises only to 27%. Most find it ugly (see chart).

Harlow, a Tory-Labour marginal in Essex, is more representative. The unemployment rate, income level and ethnic mix in this scruffy post-war new town are similar to the national averages. It is no metropolitan bubble. UKIP won five council seats here in May and locals have all the usual grumbles about modern Britain. But, unlike UKIP’s strongholds, the place has buzz—shoppers bustle, traffic clogs the roads near the station as commuters spill out of trains from London. Most people in Harlow look to the future more than they cling to the past. Carol, a divorced grandmother, frets about her grandson’s university prospects. A Lithuanian waitress says most locals are welcoming. Sandra, a young mother who has just moved onto a newbuild estate with neatly mown lawns, says it is a good place to bring up kids. Places like Harlow dictate election results. In all but one since 1955 the party that took the constituency won nationally, too. Upwardly mobile working-class voters there contributed to Margaret Thatcher’s big majorities in the 1980s and gave Tony Blair his Labour landslide in 1997. Gavin Callaghan, Labour’s candidate in Basildon, another Essex bellwether, cites his parents as typical local voters. A cabbie and a bank clerk, they moved out of east London in 1988 so they could buy a house. UKIP’s resentful messages jar with such aspirational folk: “Attacking the rich, the poor and immigrants is bad politics. People who are ambitious for themselves and their families feel left out,” he says. Jordan Newell, the Labour candidate in nearby Colchester, agrees: “Talking about UKIP’s issues means not talking about those that matter to the majority.” Polls suggest he has a point. By far the most important subjects for Britons are the economy and health care, not immigration. Even in the first part of the current parliament, average voters were telling pollsters that the Conservatives were far to the right and Labour far to the left of them (more so than in the last parliament). They still do, and UKIP’s recent rise has sharpened the dilemma—tempting the parties to concentrate on their leaky traditional bases rather than winning over Middle England, as Thatcher and Mr Blair did in their time. With just seven months until the election both parties seem engrossed in energising those bases. Neither looks capable of winning a commanding parliamentary majority. That is good news for the centrist Liberal Democrats who, though unpopular after four years in coalition government, are hoping to hold seats like Colchester.

It may be too late for either the Tories or Labour to make a breakthrough, and UKIP is not going away any time soon. But that should not make chasing voters who have defected to the party their priority. Some of the defectors will return to the fold as the election campaign illuminates UKIP’s shaky policies and internal rifts. Others are probably gone for good. By contrast the centrist majority is large and biddable. Robert Halfon, the Conservative MP for Harlow, seems to have hit on a sensible formula for wooing it: campaign doggedly on aspirational, pocketbook issues like fuel prices, apprenticeships and home ownership. His moderate targets, quietly getting on with their lives, may be less volcanic than Mr Farage’s protest voters. But every five years they decide who runs Britain.