Rochdale makes its mark at last, to the regret of Mr Brown

Rochdale is somewhere people tend to come from, not go to.

From Gracie Fields, the Thirties music hall star, to Andy Kershaw, the aberrant DJ, the place is more famed for its exports than for its indigenous culture. This is a town whose football team have never played above the third tier of the English league. When you arrive, official signs pronounce: "Rochdale – it's happening". But you could have been forgiven for feeling otherwise.

Not any more. For this is the ordinary place where an ordinary grandmother left her ordinary home – mid-terraced, ivy-clad, with wind chimes from Minorca – and created what could turn out to be the pivotal moment of the 2010 election campaign, dealing a grave blow to Gordon Brown just as he hoped to be on the point of rallying to return to Downing Street.

Gillian Duffy went out to buy a loaf of bread and returned home having done great damage to the political career of the Prime Minister, having raised concerns about immigration from eastern Europe and been branded by the Labour leader, forgetful of his lapel microphone, as a "bigoted woman".

The locals are proud of her achievement. "She asked perfectly valid questions," John Sutton said. "She was honest, upfront and to the point." "If she's a bigot, so am I," said another Rochdale resident. "Mrs Duffy is a hero of the election, said Mr D Ashworth.

On the blog of the Rochdale Observer, a woman from the other side of the town came forward to support her, claiming: "Almost every time I visit a post office or a cash dispenser I am badgered by Eastern European women carrying babies, begging for money and thrusting handwritten notes under my nose claiming they are homeless and without food.

"It is becoming tiresome, but however impoverished they are, the same people can be seen in the local café some hours later, using mobile phones and smoking cigarettes. They are beggars, plain and simple. They also happen to be Eastern Europeans. Perhaps that is the root of Mrs Duffy's quite proper question."

Local irritation over immigration is on such a scale that it could impact upon this highly marginal seat.

The town, which was a cotton boom town of the Industrial Revolution, and the birthplace of the Co-operative Movement, has long veered between Labour and the Liberal Democrats.

For two decades, the seat was held by the larger-than-life Liberal MP Cyril Smith – reportedly, at 29 stone, 12 pounds, the heaviest British MP ever. In the early years of New Labour it was occupied by Lorna Fitzsimons, designated a "Blair Babe", but she lost the seat to the Liberal Democrats in 2005.

It could easily have gone Labour's way this time. The incumbent MP, Paul Rowen, came in for a deal of criticism in the MPs' expenses scandal. "He's about as useful as a chocolate fireguard," one local opined.

Now Gordon Brown has thrown him a lifeline. Bigotgate, Mr Rowen delightedly proclaimed yesterday, was "the beginning of the end" for Mr Brown.

His party leader, Nick Clegg, took time out from his leadership debate preparations to send a message to Rochdale voters, announcing that the first Cleggs had apparently come from nearby Littleborough in the 12th century, which made him "in a sense" a local himself.

But immigration is not an easy call for Mr Clegg. "At least Brown only insulted one Rochdale lass," one local blogger complained, but Nick Clegg "insults all hard-working, honest people by offering an amnesty to all illegal immigrants."

"Stop being used as voting fodder by the old-gang parties," another denizen of the webworld pronounced. "Vote BNP."

The outcome is as hard to read here as elsewhere. There are some who are impatient with all the scapegoating of immigrants. Economic migrants from the EU came to do jobs that the workshy, benefits-dependent class refused to do, said Charles De Mar of Lower Fold in Rochdale. "Why were our home-grown boys and girls not doing them? I'd love to know."

Another said: "Gordon Brown was right to call this woman a bigot. He's got my vote now." A third agreed: "He's gone up in my estimation."

Why was Mrs Duffy, who was so keen to exercise her right to free speech in public, so shocked when the PM exercises his in private, asked Dave Kinkladze. He should have stood by his comments, said another local.

But most of the Rochdale electorate appear to have other instincts. At the last election, 40 per cent of the town simply didn't bother to vote – one of the biggest percentages anywhere in the UK. Their number may grow this time. And Gillian Duffy, until now a lifelong Labour supporter, may well join them.