Grey men can touch up their streaks, straddle a motorbike or lose the tie and it's called a midlife crisis. When a political party leader, whose popularity is flatlining changes his style, he risks being seen as more desperate than vain.

Labour leader Phil Goff appears to be reinventing himself as routinely as the seasons change in an attempt to strike a chord with voters.

The dyed hair, which stole the limelight at Goff's State of the Nation speech in Auckland this week was an obvious attempt to look younger, even if he belatedly claimed his wife, Mary, put him up to it. There's an election at year's end and, to a fresh crop of 18-to-20-year-old voters, there's no such thing as a youthful 57.

One of Goff's problems is that he is a known quantity, a political journeyman taking over from a leader, Helen Clark, who won respect for substance over style. It's worth remembering that voters took some years to warm to Clark, who also resorted to makeovers.

Goff is no doubt getting plenty of advice. His even-handedness can seem robotic. He may be passionate, but he doesn't show it. Some wish he would simply lose his temper, or show he has a pulse, occasionally.

That assiduous observer of political fads, Herald columnist John Armstrong, has charted Goff's efforts to reposition himself with voters.

There was Biker Goff, who arrived at Labour's 2009 conference on a Triumph - an attempt, insiders said, to show "he wasn't just a suit". A year later conference-goers saw a huge banner of Goff wearing a cheesy grin and a white open-neck shirt, hands in pocket to look casual. Armstrong commented: "This is Relaxed Goff the party wants the public to see - not Robo-Goff."

Some see his latest persona as modelled on a young Tony Blair, others say he looks more like John Key, in a deliberate bid to blur the distinctions between his younger, more popular rival.

PR adviser Deborah Pead can't see voters turning off Goff over the colour of his hair. She points out that New Zealanders are hair-obsessed, spending $150 million a year on professional colouring.

"I think it gives him a youthful image. Good on him for showing he cares about his looks. When you look good, your self-esteem is higher and it gives more confidence."

Indeed, there is science, albeit political, behind the image-tweaking. Associate Professor Claire Robinson of Massey University has followed leaders' attempts to change perceptions since a softly backlit image of Clark, teeth straightened and whitened, was unveiled in 1999.

"She looked really glamorous and most people hadn't thought that about Helen Clark," says Robinson, an expert in political marketing.

Robinson says there's evidence that attractiveness does make a difference in a politician.

"There's this halo effect - an attractive politician is assumed to be credible and trustworthy, so it's important to not look terrible.

"But the more people get to know a politician the less important appearance is."

After 30 years in the public eye, it's far too late for Goff to become someone he's not, she says.

Changing your hair colour at Goff's age is unusual "unless you are really desperate, and that's so not the message he needs to be conveying at the moment."

There are other things he could be doing, she says. Rather than allow caucus colleagues to speak on portfolio issues, he should be the spokesperson on every issue.

"What that says is he is on top of every issue and he has a solution to every issue.

"To compete against someone as supremely popular as John Key he has to show that he is as on top of the issues, if not more so. And he has to be the only person speaking for the Labour Party.

"He has to start focusing on the relationships he has with people - how he relates to voters in their homes, how he relates to interviewers, and prepare for the debates he has with Key and how he will sell himself in the campaign."

Goff can come across as negative in the middle of interviews whereas Key remains optimistic and offers solutions, she says.

He needs to make eye contact. "Helen Clark was very good at the direct stare portrait - he hasn't got there yet.

"Political advisers tend to focus on the soundbite but in fact it's the image bite that's more important."

Goff could also capitalise on perceptions that he has more substance than Key.

"It's kind of sad to watch him go through so many appearance changes in such a short time and it does ring slightly of somebody who's desperate to find whatever it is that people will respond to.

"In fact, leadership impressions happen over a long period of time."

PR adviser Jenni Raynish, whose clients have included the National Party, suggests the hair dye made a convenient distraction from Labour's hard-to-sell tax policy. "In an election year if your policy is problematic it's a great way of staying in the news."

Raynish suggests Goff's biggest problem is the legacy of Helen Clark and he needs more time to establish himself.

"He should just keep on communicating about what he believes in because the memory of Helen Clark is fading over time."

Goff might also argue he is following Labour traditions. Well before Clark, leaders Norm Kirk and David Lange were persuaded to remodel themselves to become more electable. They became Prime Ministers.

"Kirk and Lange were very big men who were not very mindful of their attire," says Bob Harvey, the former advertising guru and Labour Party president who advised both.

Kirk was eased into snappier suits and introduced to a comb. Lange's transformation went as far as stomach-stapling (in part for health reasons) in 1982.

Harvey says it's a different game now, in which elections are won and lost on television and in mall walkabouts.

"It's charisma and your ability to work an audience - the whole thing is way beyond hair dye. "It comes down to the camera - either you have a style that fits or you do not."

Harvey says Goff has done well to cultivate a "Blair-like image, youthful and vigorous."

"What he needs is a decent story. The script has got to be good, and the person that delivers it has to be 100 per cent credible."

Political commentator Denis Welch says leaders need to find their level and stick with it.

Helen Clark was perceived as being "not quite there" as a leader until she beat off a leadership coup in 1996, says Welch, author of Helen Clark: A Political Life.

"I think Goff is mistaken in trying to be as matey and nice and blokey as Key - the public has got a nose for that kind of insincerity.

"I don't think he's ever quite found his level of being comfortable enough with being who you are and projecting that image.

"Clark took a long time to find it and when she did we all voted for it."