The wife of Barack Obama, the presidential candidate who is tussling with Hillary Clinton to become the Democratic choice to succeed President Bush, is to give up her job to play a full part in her husband's campaign.

Michelle Obama, a senior executive at the University of Chicago Medical Center and, like her husband, a graduate of Harvard Law school has been gradually emerging as an increasing presence in Mr Obama's attempt to become America's first black president.

In an interview with The Washington Post today she admitted "it's a bit disconcerting. But it's not like I'll be bored", as she discussed the role she intends to play in a presidential contest where candidates' other halves — in the form of Bill Clinton, the former president, and Elizabeth Edwards, Jonathan Edwards' wife, who has breast cancer — are expected to hold a significant measure of influence over voters' choices.

Mrs Obama, who earns more money as a hospitals' vice-president than her husband, the junior senator for Illinois, has been compared to a younger Mrs Clinton because of the significant backstage role she is believed to play in his campaign.

Mr Obama calls her his "true north" and says she runs their young family — they have two daughters — "with a general's efficiency". According to a recent New Yorker profile, Mr Obama has a habit in speeches of saying that that whenever he has faced a big decision in his life: "I did what every black man does when confronted with a major decision... I prayed on it, and I asked my wife."

And in recent weeks Mrs Obama, who is tall and striking, has also deployed alone on the campaign trail, making speeches in churches in Illinois and Carolina. In a letter sent to potential donors earlier this month she wrote: "I'm now one of those 'other' kind of people Barack talks about — the people who believe democracy can live up to its promise, who are not just willing to do their part to make it work but who are enthused about the prospect."

The couple met when Mrs Obama was given the job of mentoring Mr Obama at the law firm where she worked in Chicago in the early 1990s. She told the Post today that she was reluctant to date the only African-American lawyer at the firm but was won over when he took her to a training session for community organisers on the south side of the city.

"People found something real and authentic in what he was saying, and it resonated with me," she told the newspaper. "And I knew then and there that Barack Obama was the real deal."

Recounting the same meeting in her recent campaign letter, Mrs Obama wrote: "He gave the most extraordinary speech I'd ever heard -- a speech about the world as it is and a speech about the world as it should be and could be. A chorus of 'amens' filled the church as he spoke. By the time he was finished he had connected with every person in the building — including me."

During her interview with the Post, Mrs Obama, who is 43, steered clear of the kind of controversial remarks the Clintons made when Mr Clinton was making his first bid for the presidency — the promise of "two for one" and Mrs Clinton's remark that she wasn't the type of woman to stay home "baking cookies". Although she did concede: "Yeah, you know, cooking isn't one of my huge things."

She wouldn't even rule out returning to her $275,000-a-year job should her husband win the White House. "Barack and I have lived very separate professional lives," she told the newspaper. "He's done his thing, I do my thing. And my focus is on figuring out what's the right thing for me to do given where I am in my life, where my kids are. And I won't know what that looks like in '08 — it changes."

Mrs Obama also chose to avoid what has been her chief oratorical tactic of the campaign so far: jokingly bringing her ethereal and cerebral husband down to earth and chiding him for his forgetfulness around the house. In her campaign letter, she added a folksy "PS" which recalled Mr Obama calling her to tell her about a nuclear non-proliferation bill and her saying: "That's nice but we have ants in the kitchen and you need to pick up some ant traps on the way home."

American commentators, such as Maureen Dowd in The New York Times, have questioned whether the tactic of portraying her young, albeit inspiring, husband as pleasantly mindless is a good idea. "The Obamas are both skeptical of hype," she wrote last month. "Michelle drily told a reporter at her husband's Senate swearing-in that perhaps someday, he would do something to earn all the attention he was getting."

"But it may not be smart politics to mock him in a way that turns him from the glam J.F.K. into the mundane Gerald Ford, toasting his own English muffins. If all Senator Obama is peddling is the Camelot mystique, why debunk the mystique?"

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