But the scope of responsibility in politics these days extends to family members, and the messes are now so numerous that by the time Barack Obama sets foot in the White House, everyone in his entourage will have to grab a mop.

That includes the first lady, who throughout the campaign demonstrated that she not just understood the power of clothes to transmit a message, but a readiness to adjust that message as the need arose.

Michelle Obama was not alone in that; Cindy McCain notably tweaked her image as the campaign ground along.

Yet Michelle Obama did something bolder on the campaign trail and, in a sense, less expected. With flashcard clarity, she signaled an interest both in looking stylish and also in advancing the cause of American fashion and those who design and make it. She wore off-the-rack stuff from J Crew and, at times controversially, designs by fashion darlings like Isabel Toledo, Thakoon Panichgul and Narciso Rodriguez. She brought to the campaign a sophisticated approach to high-low dressing, a determination to adapt designers’ work to suit herself as well as a forthright conviction that it is the woman who should wear the clothes and not the other way around.

Insignificant as this may seem in the larger scheme of things, it is less so when one considers the distressing state in which American fashion has found itself lately, with both chain and department stores shutting their doors, consumer confidence at its lowest level in decades and manufacturers struggling to remain afloat.

Hamish Bowles, the Vogue editor who was curator of Jacqueline Kennedy: The White House Years, a 2001 show of Kennedy’s style at the Metropolitan Museum of Art, said of Michelle Obama, “My perception is that she’s already had an extremely potent effect” on the business.

“Just looking at the designers she’s been drawn to, you can see she’s shown astute sartorial judgment,” Bowles said. What she has also made clear in her choices, he added, is “that thoughtful and intelligent American designers are perfectly capable of creating clothes that have an impact on the world stage.”

“What the first lady wears has a lot of effect on the industry, absolutely,” said Arnold Scaasi, who began designing clothes for the wives of American presidents during the term of Dwight D Eisenhower.

Three days before the inauguration, Michelle Obama will turn 45. Yet like her husband she conveys a more youthful impression, and her vital appearance has a lot do with her particular appeal to the fashion industry.

“She’s like 25 years younger than the last few first ladies, and her age opens her up to a more youthful approach,” the designer Anna Sui said. “I loved her choice of Narciso,” she added, referring to the designer Narciso Rodriguez, whose dress Michelle Obama wore, in a version she adapted from the runway original and customized with a cardigan sweater, on election night.

“She could potentially do what Jackie did, bring about a new awareness and a fresh outlook, just by not being so intentionally ‘first lady,’ by mixing designer things with off the rack,” Sui said. “She can give a big boost to the American fashion industry — and we need all the help we can get.”