IT was the delicately named Lady Bird Johnson who, with steel in her adoring smile, observed that a politician should be born a foundling and remain a bachelor, an eloquently piercing choice of words that says much about the imprisoning role of America's First Lady.

Now, as the world heaps frantic expectations on the noble but untested shoulders of the man destined to be the 44th President of the United States, Michelle Obama knows that she, too, is walking into a near-impossible task: that of preserving a private and cherished family life when an invasive media, plus security demands, are primed to mock that very commitment as being hopelessly naive.

The First Lady in waiting has already demonstrated her credentials as an independent spirit. Her demonstrations of keen intelligence and articulacy during the election campaign didn't stop short of reminding those who would deify her husband that Barack Obama was not the new, fix-it-all messiah.

Will her skin be thick enough to withstand constant, impertinent elbowing aside by White House aides who insist on first claim to the president's attention?

The American vice-presidency is generally perceived as the most thankless job in the White House, but its frustrations are nothing compared to those of the First Lady.

Lady Bird Johnson's astute judgment on politicians may have contained suppressed resentment at her husband's amorous peccadilloes, but she was also shrewd enough to know that her survival in the chauvinistic climate of the White House during the 1960s depended on her accommodating the system, not fighting it.

So she applied her Southern charm to genteel pursuits such as a national plan to revive meadow flowers, and left the noisier rights of women, and the wrongs of men, conspicuously off her agenda.

Lady Bird, of course, had taken over from a First Lady traumatised by the assassination of her husband, JFK, whose shattered head Jackie Kennedy had cradled in her lap on that fateful day.

But it wasn't just the horror of that event or Lyndon B Johnson's subsequent ruinous overseeing of the war in Vietnam that made Lady Bird determined to be low-key. As the wife of Kennedy's vice-president, she had carefully observed Jackie's short but potent reign as First Lady from 1961 to 63, and its difficulties were clear.

None of Jackie's forerunners had possessed her poise and intellect, yet even that combination had not saved her from the macho rudeness of the Oval Office and the persistent muttering of begrudgers. Jackie's glamour and intelligence appealed but also repelled, and she was the target of insults from those who believed her high tastes were out of place in "classless" America.

But the very idea that the US was classless in the 1960s was a fallacy. Then, as now, two elements comprised society: the very rich and the very poor. Much later, through the 1980s, Nancy Reagan pursued endless photo opportunities with all manner of human casualties, but even that couldn't conceal her hunger for the careless dazzle of triumphalism.

She believed luxury came with the job of First Lady, and since her hold on the president was too strong for foes to break, they aimed their knives at her White House profligacy.

Something similar befell Abraham Lincoln's vivacious and impulsive wife, Mary who, from 1860 to the year of Lincoln's assassination in 1865, felt that her First Lady status was filled more with misery than accomplishment.

Mary ornamented her crisp intelligence, natural grace and love of finery with the polished wiles of a Southern coquette. She entertained lavishly, hoping that this might bring conflicting sides together. But, as the civil war dragged on, her extravagance was branded unpatriotic. And while the South denounced her as a traitor to her roots, those loyal to the Union suspected her of treason.

Yet when Mary abandoned entertaining, after the death of her son Willie in 1862, those same critics accused her of neglecting her social duties.

Thus a certain Catch-22 became embedded in the office of First Lady: whatever the unelected incumbent does, she will never please all of the people all of the time.

In the 1790s, George Washington's personal secretary created a rigid protocol for his wife, Martha, America's first First Lady who found her eight years in the role extremely disagreeable. Pursued even in those days by the press, and virtually unable to meet her oldest friends, she experienced the kind of internal loneliness that has partly defined the job ever since.

Generations later, in the 1930s and 40s, Eleanor Roosevelt steered the status of First Lady in an entirely new direction. Born into American aristocracy in a family ravaged by drink and self-destruction, she was both a visionary and political activist, her bold endorsement of equality and human rights making her one of the most influential figures to shape American democracy. Not for nothing did Hillary Clinton, 46 years later, regard Eleanor as her most significant mentor.

For Mamie Eisenhower, in the 1950s, and Betty Ford, in the 1970s, their time in the White House brought only desolation, both driven into the swamp of alcoholism in the futile hope of escape. Betty found salvation in bravely "coming clean" and pioneering America's rehabilitation movement.

For Mamie, though, drinking was her response to all of those who won her husband's attention ahead of her, and her " poor nerves" were the official excuse for her many public absences from Dwight Eisenhower's side.

"A doll's terrifying pose" was how one political commentator described Pat Nixon's stance as First Lady in the 1970s, when the wreckage of the Watergate scandal shamed her husband's presidency.

Through it all, and listening to Richard Nixon's glowering litany of shifted blame, she used that patient, tortured gaze to hold the media at a distance.

So, how will Michelle Obama handle her time at 1600 Pennsylvania Avenue? During her husband's presidential campaign she was careful to stress that she was not one of his senior advisers, and careful also to keep her promise to their children - Malia aged 10 and Sasha, aged seven - that she would only be away from home one night a week. And, apart from insisting that her first job as First Lady will be First Mom, she has been cautious about defining how she sees the role.

It's likely, though, that she will continue the dialogue on race and education that she began with the nation during the campaign, using motherhood as the framework.

In the run-up to the inauguration, the White House guard reportedly advised her to cool her tendency for ironic humour, which can be seized on as sarcasm. But it should be remembered that Michelle already knows the score.

After all, her first date with Barack Obama was to the cinema. And the movie? Spike Lee's Do The Right Thing.