To his wife, Sarah, he is "DH" – dear husband – while his friend Piers Morgan attempts to portray him as a brooding, but romantic, Mr Darcy. To some former Downing Street staffers, he is a foul-tempered monster who, according to ex-Labour spin doctor Lance Price's new book, "is psychologically and emotionally incapable of leadership of any kind".

These descriptions of Gordon Brown were all offered in the past week, and are all variations on old themes. Which is more accurate is a matter of debate. What is clear, as The Independent on Sunday's poll shows today, is that more voters than, say, a year ago, believe the Prime Minister has a "warm human side". Fifty per cent of people agree with this statement, while 43 per cent disagree. Among women, the figure is higher: 55 per cent agree. Even 38 per cent of Conservative voters believe he is warm.

Aides describe his TV interview with Morgan, broadcast on ITV today, in which he cries over the death of his daughter Jennifer, as a "watershed moment" for the normally private PM. While the tears are too much for some, Mr Brown's appearance is the culmination of a project to "humanise" him, and the poll figures show it is working.

In part, Mr Brown's standing has improved because of his own actions. His jokes, for example, have become funny. Last month, at the Fabian Society conference, Mr Brown cracked an apparently off-the-cuff and self-deprecating joke that even he couldn't remember the five tests on the euro.

But the project would not have worked without the help of Mrs Brown and two of British politics' grand masters of communication and spin: Alastair Campbell and Lord Mandelson.

It was Mrs Brown who persuaded her husband to appear on Morgan's Life Stories, an hour-long interview in front of a studio audience – although both Mr Campbell and the Secretary of State for Business were fully behind the move, Morgan revealed yesterday. The journalist told the IoS: "I had asked him three or four times and he'd said no, but then they went away at Christmas and he and Sarah talked about it and about other things they might do in the run-up to the election, and after that he said yes."

Members of the audience were asked to come up with words to describe the Prime Minister, he said. They came up with three very unflattering labels: grumpy, knackered and plonker, and a surprising one: delectable. Morgan added: "When I put the word 'plonker' to him, he answered 'well, you'd know about that Piers'."

Mrs Brown's well-documented ability to put a soft gloss on her husband's "grumpy" exterior was enhanced last week when she spent an hour "chatting" on the Mumsnet website, the 2010 election equivalent of GMTV and This Morning interviews of 1997.

The project to humanise Mr Brown has developed since he became PM in July 2007, but was stepped up when Lord Mandelson returned to the Cabinet and Mr Campbell became more involved. The departure last April of Damian McBride, the No 10 adviser, created less divisive press briefings, and the atmosphere inside Downing Street became less toxic. When things get tense, Lord Mandelson lightens the mood by "taking the mickey" out of Mr Brown.

A turning point came in November, when The Sun attacked Mr Brown over his misspelt letter to Jacqui Janes, the mother of a soldier killed in Afghanistan. The public's sympathy was with the PM, with just two dozen out of around 1,000 messages sent to No 10 critical of him.

Among the softer revelations last week is Mr Brown's appetite for fruit. In an echo of the revelation that Margaret Thatcher ate four eggs a day when she was campaigning for the 1979 election, we learnt that Mr Brown eats nine bananas a day. But is the public being fed an inaccurate image of the PM?

No 10 aides deny recent newspaper reports that Mr Brown hit a male official, and insiders claim that he only gets angry when there is "justification" and it is "never personal". Yet there is nevertheless apprehension inside Downing Street at the forthcoming publication of The End of the Party by Andrew Rawnsley, which is rumoured to detail incidents of Mr Brown's foul temper. Mr Brown was, it is understood, furious when, during a visit to Washington last summer, it was reported that President Barack Obama had snubbed him.

No 10 insiders claim Mr Brown is best when he is authentic – citing Lord Mandelson's quote last month that "there's no airbrushing Gordon Brown like David Cameron". One insider said: "If we told him to emote, well, it doesn't work like that. That's not who he is."

But was the PM really being true to himself when he bared his soul to Morgan? Few who watch his red-rimmed eyes today will fail to be moved. Yet the timing, weeks before what will be a bitterly fought election campaign, is unsettling.

Mr Brown has an election to fight, and he is up against a Tory leader whom voters see as an emotionally intelligent, if slick, politician. Mr Cameron's wife, Samantha, may soon follow Sarah Brown on to Mumsnet. Just like the leaders' election TV debates, today's interview is high risk for Mr Brown, but his friends believe it is a risk worth taking.

The public mood: Could it be The Sun wot wins it for Labour?