Picture in your mind's eye a vision of the White House's first lady, and there's every chance you've conjured up one or all of the following: impeccable tailoring, rictus grin, affably standing shoulder to shoulder with ostensibly the most powerful man in the free world. The woman who is the docile, devoted wind beneath the president's wings; a role that's more that of protector and facilitator than anything else.
Yet history tells a different story, and the White House has seen more than its fair share of redoubtable, powerful women.
In the week of 94-year-old Nancy Regan's death, the world was prompted to doff a cap to her not-insignificant influence on her husband Ronald, not least in his declining years. As the 40th president's health ebbed away due to Alzheimer's, Nancy was credited as being central to his successful term as president.
It could be argued that Nancy initially made a negative impression on the US; while the country struggled under an unkind economic climate, Nancy soon hit the headlines for her lavish parties, her hostessing skills and for remodelling the White House at significant cost (a precedent likely set by the very first presidential wife, Martha Washington). Also not helping her popularity was Nancy's hiring of an astrologer, something that rankled the media, along with her husband's improbable career trajectory from actor to politico.
But in the wake of her death, Nancy has been credited with more than just that. USA Today noted how she "softened her husband's sharp edges to produce a pragmatic president who could cut deals with the political opposition in Congress and Soviet leaders he had assailed".
It's true that Nancy was thought to be the impetus behind the president's reaching out to the Soviets, and the eventual end of the Cold War and dissolution of the Soviet Union.
Her influence was felt keenly elsewhere, not least on domestic policy, where a word in her husband's ear meant that certain programmes for America's poor were preserved.
There were other notable victories; the hiring and firing of certain consultants and aides, and masterminding her husband's reputation.
And then there was the role she took on somewhat unwillingly and entirely by dint of tragic circumstance.
Referring to Nancy's 'long goodbye' to her husband, President Barack Obama noted: "She became a voice on behalf of millions of families going through the depleting, aching reality of Alzheimer's, and took on a new role, as advocate, on behalf of treatments that hold the potential and the promise to improve and save lives."
A formidable legacy, certainly, and one that places Nancy in the pantheon of Mrs Presidents.
But soon, the question begs to be answered: how influential can a first lady - a woman who is for all intents and purposes putting her husband and his career at the centre of her life - really be?
Well, quite influential, as it happens and it's by no means a modern phenomenon.
Though never overly specified, the job spec was to play house (and hostess) at the White House, but the role evolved down the years so that first ladies were prompted to select causes to eschew.
Sara Polk (wife of 11th president James) was thought to have crafted speeches and tended to official correspondence; Abigail Filmore (wife of 13th president Millard) created the White House library; Edith Wilson (wife of 28th president Woodrow) took unofficial control over the presidency after her husband's stroke in 1919. Similarly, Rosalynn Carter (wife of 39th president Jimmy) sat in on several of her husband's cabinet meetings.
And then there was Eleanor Roosevelt (wife of 32nd president Franklin), as quotable and controversial as she was indefatigable and esteemed.
Using the spotlight, and a syndicated newspaper column, to advance causes as diverse as civil rights and women's rights, Eleanor - the longest serving first lady - was a leader in the formation of the United Nations and helped draft the Universal Declaration of Human Rights.
By the time of her death in 1962, Eleanor Roosevelt was described as "the object of almost universal respect" in her New York Times obituary.
Advocating for causes was a particular specialty for Betty Ford (wife of 38th president Gerald), too; psychiatric treatment, the legalisation of abortion and breast cancer awareness topped her agenda. People listened, not least because such candour and personal honesty from a high-profile figure was uncommon at the time.
For every Eleanor and Betty, there were others who preferred a life of familial quietude, not to mention the fringe benefits of the job at hand; namely celebrity, a coterie of fashion designers to hand, and a number of willing aides.
Jackie Kennedy (wife of 35th president, John) in particular spent much of her time in Pennsylvania Avenue restoring the White House and buffing her reputation as a poised style icon to a high shine. History would remember her as a wife who preferred not to get involved in her husband's work, and even her role in his assassination in 1963 would sadly focus on Jackie as the stylish trophy wife (several media outlets referred to her iconic Chanel suit, spattered in blood as it was).
Ever the lady, Jackie kept a dignified silence amid rumblings of her husband's extra-marital affairs: a typical reaction of its time.
Hillary Rodham Clinton (wife of 42nd president Bill) found herself in a not dissimilar situation, albeit in a rather different cultural and political climate.
Much like her predecessor, Hillary appeared to turn a blind eye to her husband's reported infidelities, prompting many to label her as a docile doormat. In truth, her power was undeniable: she was appointed the head of the task force on National Health Care Reform, and spoke openly on women's and children's issues, espousing important legislation on the Adoption & Safe Families Act.
Becoming a junior senator after her husband's second term as president, Hillary was elected to be Obama's Secretary of State after she gave him a run for his money during the Democratic presidential nomination in 2008.
So strong, in fact, that Hillary has gone in for a second bite this year, gunning for the gig as 45th president.
And this is the year that the age-old conceit of the typical first lady may well get a massive makeover. Last week's Super Tuesday (when most states vote on respective party candidates) put Clinton and Donald Trump as frontrunners in this year's race to 1600 Pennsylvania Avenue.
If Trump should end up bagging the presidency later this year, his wife Melania Trump - a Slovenian supermodel-turned-jewellery-designer - will be a force to be reckoned with as first lady.
Never mind upping the glam factor; Melania is thought to have her husband's ear. There's no doubting that the high-wattage glare of the media's spotlight will be trained on her every move. In other words, politicos may underestimate her power at their peril, should her husband reign supreme in this year's presidential scrum.
Alternatively, there's the possibility, should Clinton end up in pole position, of a first gentleman taking up residence… and even more tantalisingly, the prospect of a former-president-turned-first-gentleman. Sea changes are indeed afoot.
And there are certainly big shoes to fill, thanks to the outgoing First Lady, Michelle Obama.
A relaxed, genuine and endearing presence at the side of her husband, 44th president Barack, Michelle set aside her own remarkable law career (Michelle met her husband at Chicago law firm, Sidley Austin) and reduced her professional responsibilities by an estimated 80pc to support her husband's race to the White House.
Originally, it was thought that Michelle was resistant to the idea of her husband running for presidency, but the two struck a deal: if he gave up smoking, she would support his decision to run.
Job done on moving to Washington, the new First Lady wasted no time in getting her hands mucky, becoming an advocate for poverty awareness, nutrition, LGBT rights, pay equity, supporting military families and the health of Americans in general. Michelle's initiatives have been described as personable and intimate, bonding with military families, visiting soup kitchens and using her high profile to advance causes.
Yet there's something much more compelling about Michelle and the way she handled her two terms as Mrs President. Modern, dynamic and unpretentious, she refused to kowtow to tradition, and has been criticised time and time again for being opinionated and outspoken in a way that her fore-sisters weren't.
In fact, the only thing more interesting than seeing who might become the White House's next domestic partner is seeing what 52-year-old Michelle will do next.
The media is already enthralled with the Obamas; whether they will return to their legal careers is moot. A position of power on the world stage is very much theirs for the taking.
Yet if Michelle follows in the footsteps of those who have gone before her, it's safe to say we are in for some seismic times indeed.
Dozens of women have followed in her footsteps, but Martha Washington, wife of first US president George, essentially set the first-lady template.
Referred to as Lady Washington, Martha was a widow and a mother of four when she married George in 1759 (her husband Daniel Custis, who was said to own hundreds of slaves in Virginia, died in 1757). Content initially to live a private life, Martha followed Washington to his winter encampments and helped to keep up morale among the officers.
When the time came for George to agree to be president of the newly formed United States of America, Martha was initially resistant, but soon acquiesced.
Given that his wife had inherited a vast estate from her first husband, Washington used his wife's great wealth to buy land and slaves; he more than tripled the size of Mount Vernon.
Despite her love of hostessing, Martha had always complained of ill health and she deteriorated rapidly after George's death in 1799.
She was to die only two years later, at the age of 70.