Alan Johnson is past his sell-by date, David Miliband bookish and defensive. But the news for Ed Balls is the worst of all: “He looks like a miniature Gordon Brown.”

Labour MPs whetting their blades for a leadership contest might like to take a moment to review the findings of in-depth polling commissioned by The Times on alternative leaders — before committing regicide.

It may yet be that a footnote of political history was fashioned in Cantley Community Centre, Doncaster, by 20 voters selected to share their views by Populus, the newspaper’s pollsters.

Housewife and hairdresser, lecturer and railway inspector — the group that gathered on a rainy night earlier this month had only one thing in common: all voted Labour at the last election. Around a third remained supporters, the same proportion had switched to the Conservatives and the remainder were undecided.

The group was shown clips of Mr Brown and then the six candidates most likely to replace him, and asked to register their reactions by sliding an on-screen pointer. The 20 voters were then shown, and asked to explain, their reactions.

The results challenge many Westminster assumptions, suggesting that Labour’s best bet to fight the next election may be a relatively unknown backbencher.

Less surprising are the results for Mr Brown, whose unpopularity is exposed in unsparing detail by the graph showing an aggregate reaction. The Prime Minister starts badly and then slumps. Perhaps most wounding of all is that the only significant spike shows the group’s reaction to a reference to Boris Johnson, whose name produced an immediate positive reaction.

It was our voters’ boredom with the Prime Minister that seemed to do him the most damage when they were asked to explain their almost universally negative responses.

“He’s so monotone, he doesn’t stimulate you. He could be talking about the most interesting thing in the world but it would be hard to get excited about it,” said one middle-aged man.

If Mr Brown could not excite these former Labour voters taking the so-called Message Meter test, perhaps David Miliband could?

At first they appeared to warm to the youthful Foreign Secretary, who set out his leadership stall in the wake of the Glasgow East by-election defeat in July. They approved of his solid, if unremarkable, observation that “people are right to be concerned about crime and antisocial behaviour”. Doubts soon crept in, however, and his citing of the Institute of Fiscal Studies while discussing the 10p tax affair appeared to be a major turn-off.

A young man in a rugby shirt seemed to speak for many: “It was as if he’d just read a book before he came on the television and couldn’t wait to spew it all out.”

Some reacted against a perceived defensiveness, others identified a lack of charisma. “I don’t think I would trust him because I’ve heard it all before,” one older woman said.

Some Labour MPs have touted Alan Johnson, with his inspirational back story of ascent from abandoned child to postman to the Cabinet. The Health Secretary has scrupulously avoided encouraging would-be supporters. It is an approach this focus group does nothing to discourage.

Although Mr Johnson might fairly complain that his clip offered little chance to shine — he was shown trying to defend Labour’s defeat in the Dunfermline & West Fife by-election — the group’s reaction was the most hostile of the night. “I just lost the will to live during this one,” sighed a young woman, while another member said that he was “past his sell-by date”. An elderly man said that he was reminded of John Major and another compared him to Victor Meldrew.

Perhaps Harriet Harman, the woman who beat Mr Johnson to become Mr Brown’s deputy last summer, could go all the way? Perhaps not. Although the Leader of the House was judged to have honesty and was considered strong, she was not liked.

Ed Balls, the Schools Secretary, is quietly positioning himself for a shot at the top job once Mr Brown goes. While sticking to safe ground (tackling knife crime and terrorism), Mr Balls registered an overall positive score. As soon as he defended Mr Brown, however, he began to bomb. “He looks like a politician,” said one, prompting another to say that he resembled a “miniature Gordon Brown”. A third observed that he “always looks like he’s about to burst out laughing”.

But just as it appeared that no one could pull it back for Labour, two surprise winners emerged. Until recently it was assumed that James Purnell would not run against Mr Miliband as the “Blairite” candidate. The findings of this focus group suggest that he might want to reconsider. Uniquely among the Cabinet ministers tested, the Welfare Secretary was given a fair hearing, even when he used words such as “renew” and “vision”. One group member dismissed him as a “false, young, ambitious spin-doctor” but it was clearly not the majority view. “I quite liked him, he’s listening and actually answering the questions,” another said. “He’s direct and to the point” was a more typical remark.

But before Labour’s right wing rallies to the Purnell banner, they might take a moment to review the group’s reaction to Jon Cruddas. The Dagenham MP is not a complete unknown, having surprised many by a strong showing last year as the left-wing candidate in Labour’s deputy leadership contest. His message — that new Labour is a spent force unable to resist David Cameron’s adoption of concepts such as community — has grown in force as the Government’s fortunes wane.

In the clip shown, Mr Cruddas — who once worked in No 10 as Tony Blair’s link with the unions — was interviewed about whether pupils are tested too much. Although the group appreciated his independence — registering strong agreement when he said that British students were the most tested in the world — they continued to warm to him even as he put the other side of the case. His graph shows a steady climb and ends with the most positive scores in the exercise.

“He spoke my language. I understood everything he said,” said one man. “Honest straight from the start,” agreed a woman. Another said that he was an “average person, middle of the road” but also “more interesting” than the others. “He was owning up to things. I actually listened to him,” said one elderly man. “It wasn’t, ‘this is how it is, this is how I want it’; he was open to discussion.”

Rick Nye, a co-director of Populus, said Mr Cruddas was the “surprise package”.

“People warmed to his straightforwardness and, above all, his willingness to criticise existing government policy in the area of testing children in schools, an issue that many respondents could readily identify with. If Labour were looking for an Identikit leader who could transform their political fortunes, he or she would have to be fresh enough to catch people’s eye, frank enough to admit Labour’s past failings, trusted enough to offer an uplifting vision of the future, and strong enough to deliver on their promises.”

It’s a tall order but — judging by this focus group — it’s a contest between Purnell and Cruddas.

Times Recommends

• Tree stump 'shows image of Virgin Mary'
• BBC drops Strictly judge for younger model
• Trafalgar Square 'reduced to a spectacle'