Donald Macintyre's sketch: Normal, slightly boring, but still a threat to Ed Miliband and David Cameron

Ukip has unleashed a scary new secret weapon in Greater Manchester: an almost normal-seeming – and even occasionally slightly boring – candidate.

If deep down John Bickley is a “fruitcake, loony and closet racist” as David Cameron once described the party’s members, there is little outward sign of it. Bickley, an electrician’s adopted son who failed the 11 plus and left school with one O-level at 16 but went on to have a successful career in the music and games industries, has so far come across as rather bland (at least until the Daily Mail reported that one of his campaign’s supporters was once a “porn star”).

It’s easy to see why Bickley was picked for tomorrow’s Wythenshawe and Sale East by-election (prompted by the sudden death of the respected Labour MP Paul Goggins), despite only joining the party in 2011.

While he talks, at exhaustive length, the regular Ukip talk on immigration, benefits, diverting overseas aid to the flood victims, and Europe – despite the fact that one his less successful business ventures benefited from a £100,000 EU grant – he fits Ukip’s self-differentiation from what it condemns as the careerism of mainstream politics.

And he has local form; canvassing in Robinswood Road, in the the vast Wythenshawe council estate, he is helpfully armed with photographs of himself as a two-year-old when he lived at No 60. Which goes down so well with Hilda Riley, a young-looking 84-year-old who was already living four doors down at the time. A passionate cyclist like the candidate, she announces “I’ll definitely vote for you.”

But it’s Labour’s incumbency that Bickley is targeting. And while castigating Labour for allowing immigration to “run out of control,” the class-war tone of some of his literature wouldn’t disgrace the Socialist Workers Party. The new leaflet proclaimed that John’s father – a lifelong Labour voter – “was a trade unionist and would not even recognise the out of touch millionaires of New Labour today that pretend to represent you, the working class people.”

So new is Bickley to the electoral game that today saw his first outing in the campaign loudspeaker car, a Renault sleekly covered with vinyl in the party’s purple and yellow. “This is great,” he exclaims, testing the microphone, “I have the power.”

Seen from the car, however, pedestrians seem stolidly impassive as the candidate urges them: “Let’s get rid of this incompetent coalition. It’s time for a change, vote John Bickley on Thursday, thank you.” Or more frequently: “Time to get rid of Labour. They have betrayed the working class.”

But it’s when we dismount that you begin to see why a new poll by the ubiquitous former Tory treasurer Lord Ashcroft’s puts Ukip in second place. Wheeling her grandson in a pushchair, Debbie Mattinson describes how she and her still unemployed 22-year-old son were made simultaneously redundant by the same catering firm, and how inadequate she has found the government’s work programme in trying to find her a proper job, or advising her on how to plug the gap between having her jobseeker’s allowance stopped and her first wages.

Then spontaneously she raises Ukip’s hot button issue “I don’t think they should be coming over here and getting JSA,” she says, adding that her “feller” has been warming to the party.

Bickley himself is vague on whether immigration is really causing local unemployment and depressed wages in Wythenshawe itself, or merely perceived to be, the scapegoat for more generalised economic anxiety.

But the residents he encountered could be central casting first-time Ukip voters. Like lifelong Labour supporter Malcolm Cook, 53, who, having lost his job at Manchester Airport after contracting MS, says he will “certainly” vote for Bickley this time.

“I am really pissed off with all this immigration.” And his wife adds – about both parties: “We’ve had enough of thieves, liars and cheats.”

Even the Ashcroft poll puts Labour up 17 points on its 2010 vote and heading for an easy win tomorrow. But some of the disillusionment exposed by Ukip’s surge should worry Ed Miliband as well as David Cameron.