The new 'Mrs O'

Fashion As the president of the United States, Barack Obama will guide the ship of state, but his wife, Michelle, will be expected to steer fashion trends.

The upmarket dressmaker Maria Pinto created this sleeveless purple silk dress for Michelle Obama, whose style during her husband's campaign has drawn comparisons to the former first lady Jacqueline KeShow more

It took less than 24 hours from her husband's victory speech for Michelle Obama to be transformed from a working mother to "Mrs O", the newest member of an exclusive club: wives of world leaders. It has emerged that Vogue is considering putting Obama on its cover. She is being touted as the new Jacqueline Kennedy Onassis; there is even a website, cheekily named Mrs O, which calls her a "budding style icon" and promises to follow every detail of what she wears, and a Michelle Obama Watch site that posts every press article about the new first lady.

But her introduction was a harsh one, as commentators poured scorn on her style choice on election night: a clinging black sheath offset by a splash of bold red made by Narciso Rodriguez, an American designer, that drew unflattering comparisons to a lava lamp and a black widow spider. The swift judgement is an indication of the intense scrutiny Obama, 44, will face when her husband moves into the Oval Office in January and they take their place in history as the first black family in the White House.

Obama, the mother of two girls, aged seven and 10, may have toned down the dress by adding sleeves to the original design, but it was still a break from the safe skirt and jacket combination generally favoured by the wives of US presidents. "It was a very strong statement that things are going to change in the White House, not just in government policy but in fashion," said Alejandra Tokoph, owner of Luxecouture, a Dubai boutique that stocks designer American labels. "She will have more scrutiny because she is different, because of her skin colour, her age and her family.

"It is fair to say that Michelle Obama will be more comparable with Jackie O because she has changed fashion for first ladies. She is young, dynamic, she is a mother, supportive of her husband. She has a repertoire of things that say she will make history." Not even her choice of hairstyle escapes sociological analysis. Patricia J Williams, a professor at Columbia University's law school, has written that her "optimistically upturned flip reflects an attitude that is subtly but powerfully liberating". The new first lady could not have an afro, Williams added, because it would be considered too "subversive" by the US public.

When The New Yorker magazine put a cartoon illustration of the Obamas on its cover in July, it attracted huge controversy for the ironic suggestion that Michelle was a 1970s black radical, complete with an afro, and Barack, whose middle name is Hussein, was a terrorist. When she was a public relations executive earning $300,000 (Dh1.9 million) a year at the University of Chicago's medical centre, Obama may have earned more than her husband. But in her campaign speech, she emphasised her role as mother and wife rather than as the tough career woman who forced the hospital to award more contracts to firms owned by minorities. Her only controversial comment during the campaign - "for the first time in my adult life I am proud of my country" - was played repeatedly on television, provoking outrage.

Since then, the Harvard Law School graduate has said her focus in the White House will be to support working mothers and the spouses of US soldiers serving in the military. She will not take a role in shaping public policy, unlike Hillary Clinton, whose appearance was also the subject of unflattering comments when she was first lady. She was derided for her thick ankles and for wearing hair bands to hold back a mop of frizz.

Obama and Clinton are not the only wives of high profile world leaders whose every item of clothing is analysed in the context of their husbands' successes. Nicolas Sarkozy, the French president, was languishing in the polls until his wife, Carla Bruni-Sarkozy, underwent an image change. After her transformation from femme fatale to the epitome of chic during a state visit to London this year, Sarkozy's popularity increased.

Obama's choice of comfortable and simple clothes is quintessentially American, while Bruni-Sarkozy - who persuaded her husband to stop jogging in public because it appeared "un-French" - is nearly always photographed in Hermes. Obama, who favours the high street retailer J Crew, is said to like spending Saturday afternoons eating pizza with old friends and their children. For better or worse, those days may be over.