It was never Michelle Obama's dream to call the White House home, as President Barack Obama acknowledged in his farewell speech last week.

But now that she's leaving after eight years as First Lady, many Democrats are hoping that she'll decide to return... as president.

She couldn't be clearer that she's not interested, but it goes to show how powerful a voice she's become since she reluctantly became First Lady in 2009.

Before the spotlight

Ms Obama, then Michelle Robinson, met Barack in 1989 when they were both working at a Chicago law firm, and three years later they were married.

Barack and Michelle Obama married in 1992. ( Supplied: Obama for America )

But their career choices would soon diverge, with Mr Obama putting law and academia behind him in the mid-'90s so that he could run for office.

"Michelle was never that wild about me going into politics," he acknowledged in a recent interview.

Nevertheless, Mr Obama says she was crucial in his success, firstly as an Illinois state senator (1997–2004), then as a US senator representing Illinois (2005–2008), and finally as the Democratic nominee for president in 2008.

"I can't underestimate the degree to which having a life partner who is so grounded and so strong and steady and fundamentally honest helped," he said.

During Mr Obama's first decade in politics, Ms Obama worked at the University of Chicago and later the University of Chicago Hospitals.

Michelle Obama graduated from Princeton University. ( Supplied: Obama for America )

As she told Oprah recently in their last interview:

"I didn't just wake up First Lady. I went to law school, I practiced law, I worked for the city, I ran a non-profit, I was an executive at a hospital."

But at the end of 2008, she was handed "a role she didn't ask for", as Mr Obama described it, when her husband was elected as the 44th President of the United States of America.

Suddenly, she was thrust into the political spotlight, whether she liked it or not.

Michelle Obama was handed "a role she didn't ask for", as Barack Obama put it, when he was elected as President. ( Chuck Kennedy/Pool: Reuters )

Life in the White House

Michelle Obama has described her job as first and foremost "mum-in-chief". ( Reuters: Petar Kujundzic )

Ms Obama has described her job as being first and foremost "mum-in-chief", and she was worried about whether moving to the White House was in the best interests of her children.

Sasha and Malia, just seven and 10 years old at the time, were "doing just fine" in Chicago, she told Oprah in 2009.

But her fears were soon allayed.

"Once I saw them thriving — not just living, but thriving, happy, excited about their day and very much focused on their world — that's when I was able to breathe," she said.

Ms Obama undertook her first project as First Lady in March 2009: planting a garden on the White House lawn.

Michelle Obama helps a boy harvest vegetables in the White House garden. ( Reuters: Mike Theiler )

It was the start of her mission to promote healthy eating and tackle childhood obesity.

"The physical and emotional health of an entire generation and the economic health and security of our nation is at stake," she said in 2010, while launching her Let's Move initiative which promotes exercise and better food choices in schools.

Nicole Hemmer, an academic at the University of Virginia and the University of Sydney's US Studies Centre, says there is "no doubt" that Ms Obama has played a role in reducing childhood obesity in America.

She says her policy focus complemented that of the president.

"While her husband worked on reforming America's health care system, Michelle Obama focused on the voluntary side of health care," she said.

Michelle Obama's Let's Move initiative promoted exercise and better food choices in schools. ( Reuters: Cheryl Gerber )

Legacy as first lady

In many ways, Ms Obama was in the tradition of previous first ladies: she was a style icon like Jackie Kennedy, and she was a partner to the president on policy issues.

But Ms Hemmer says if there's one way in which she broke from the mould, it was in her role as one of the strongest moral voices of the Obama administration.

"Her speech at the 2016 Democratic convention, as well as her speech following Trump's Access Hollywood tape, were sharp, moving, and both intellectually sharp and morally precise. No wonder both went viral," she said.

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Nevertheless, Mr Obama told 60 Minutes in one of his final television interviews that his wife "never fully embraced being in the public spotlight".

"Which is ironic given how good she is," he added.

Ms Hemmer says Ms Obama will be remembered as an "intensely private First Lady" who protected her children from the media's gaze.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 5 minutes 52 seconds 5 m Lateline looks at the legacy of Michelle Obama

She's not coming back

In her last speech as first lady, Ms Obama said it had been "the greatest honour of my life".

"It's nuts. I feel like crying right now," she told Jimmy Fallon during a recent appearance on his talk show.

"I didn't think that it was going to be that emotional, because it's like, yeah, we're ready. We're good. We're ready to go."

Late last year, a WSJ/NBC poll found Ms Obama was the most popular political figure in American federal politics, more popular even than her husband.

But she says she won't be returning as president. This is what she told Oprah recently: