It is rare that one envies the American political process. But what a blast to live in New Hampshire this week, to join the doughty diner waitresses (played in the movies by Susan Sarandon) as they ripped off pinafores, the soccer moms hurriedly U-turning their station wagons, the first wives and lapsed feminists blinking awake and all heading as one to the polling booths to stake their sisterhood on Hillary Clinton.

“You go, girl!” - that high-fiving excitement and pride in another woman's chutzpah and talent - is not a British battlecry. What woman politician here engenders any affection from her own sex, let alone could win - like Mrs Clinton at that primary - 70 per cent of all female voters over 40? Sure, the tears helped, yet Ruth Kelly, Theresa May, Tessa Jowell, even Harriet Harman, who has made women's betterment her entire life's work, could all cry us a river and no one would chuck them a tissue.

The struggle of ascending to high political office seems to suck out of British women their most appealing qualities: earthiness, honesty, spontaneity, informality. Few women ministers appear comfortable in their skin, just puzzled how to look, how to speak, how to be. They sound more irksomely apparatchik than men when drilling the party line on Question Time. They adopt the ill-fitting skirt suits of power because they fear anything expensive, elegant or hip will throttle their gravitas. A prospect that does not trouble female European ministers, nor a legion of effortlessly chic British women in banking, business or the arts.

Women politicians are no draw for women voters, who think them either patronising or odd; instead they are reading subtler messages to decide their allegiance. The greatest triumph of David Cameron's leadership so far is to give permission for a certain type of female voter - youngish of heart if not years, fashionable, materialistic, liberal, educated and sharp - to contemplate voting Conservative. Let's call her Grazia Girl after the magazine whose “shoes and news” agenda is pretty much the sharpest reflection of what the modern female head currently contains.

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That women judge on appearances does not betoken a shallowness, more a highly tuned antenna for semiotics. I know, for example, I could never be bosom buds with anyone whose house had ruched knicker blinds. A friend of mine, certainly no bimbo, voted for Justine Greening, now Tory MP in Putney, after seeing her canvass in a foxy leather jacket: “She looked like one of us,” was her simple reckoning. And in the lower Tory ranks are women like Louise Bagshawe, Priti Patel and Harriet Baldwin, who don't resemble the geeks or monsters or single-mother haters who thronged a Conservative women's conference I attended just three years ago.

But the biggest green light for Grazia Girl is Samantha Cameron, who so completely shares her aspirations: not just for vague notions like healthcare and education, but specific things like having a £950 Smythson Nancy bag and a husband who kisses you with a cool “love you babe”. While Cherie Blair embodied the frantic having-it-all working motherhood circa 1997, Sam Cam displays the lighter yet no less serious, shoulder-pad free, gender-blended modern marital deal. That Sam cooks Jamie Oliver recipes, has a messy kitchen and shops at Zara somehow reassures us that her husband won't asset-strip the NHS or close down nurseries.

Mr Cameron has neutralised fears around public services not through policy or speeches but personal lifestyle; actually being seen to use them. Even if his daughter is likely to attend St Mary Abbots in Kensington Church Street, so white, middle-class and self-selecting it might as well be private. How extraordinary then that, according to a recent poll, we now think a Notting Hill-dwelling Etonian married to an heiress cares more about ordinary people's problems than a Labour Prime Minister. There is now no vampires-emerging-from-the-crypt terror at a Tory return to power, not even on the Left.

Gordon Brown must wonder at the fickle ingratitude of Grazia Girl, who has benefited so much from Labour policy. But how can he win her back? His political agenda over the past year has been so darkly masculine, so clunkingly authoritarian - new prisons, anti-terror measures, detention without charge - that it has little female appeal.

Moreover, he keeps his own personal story so determinedly hidden that, in contrast with the Camerons, it invites suspicion. I still hear people speculating that the Brown marriage must be a joyless sham. When I say Mr Brown drives halfway across the country just to make sure he can spend the night with his family, that I've seen them together and they are relaxed, teasing and affectionate, sceptical eyes are usually rolled.

Of course, Mr Brown's determination to keep his wife and children out of the picture, not to milk the humanising opportunities of, say, discussing his younger son's cystic fibrosis, are entirely admirable. It is just Mr Cameron, who allows cameras into his kitchen, is forever photographed manning a buggy and talks easily and powerfully about his disabled son, better represents the everyblogger generation of Facebook, Flickr and MySpace where a person's every thought and intimate moment can be freely scrutinised online.

So far all attempts to winkle Sarah Brown out of her natural reserve have been resisted. From her stilted waves and doubtful smiles as she awkwardly kisses her husband, she is clearly photo-call phobic. And her every public performance is haunted by the spectre of a gurning, clingy, pixy-boot-wearing, ultimately reviled Cherie Blair.

And yet Sarah Brown could also be her husband's most powerful weapon in this political lifestyle war. She may not be a society fashion-plate like la Cameron but she has plenty that women voters will admire: seriousness, integrity, she endured losing a child with great public grace, and motherhood has warmed her naturally cool disposition. Why must the Prime Minister's wife, particularly a clever, fast-talking media professional like Sarah Brown, live in public silence? American political spouses have never played the silent starlet simply because they fear one interview will unleash the media beast: Laura Bush held her own election rallies and was more warmly cheered than her husband.

Gordon Brown could learn a lot from Mrs Clinton's political resurrection in New Hampshire: seriousness, intellectual weight and experience are not enough: voters, particularly women, require a flicker of humanity from their leaders.

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