Today she will need to do exactly that. Never before has the wife of a sitting president been summoned before a grand jury. The experience is unnerving, even for a formidable lawyer such as Mrs Clinton. A grand jury does not deliver verdicts. Instead, its 23 jurors decide whether charges should be brought. Hillary Clinton has not been notified that she is a "target", meaning that the independent Whitewater counsel Kenneth Starr is not considering indicting her - for now at least. Starr has been investigating the Whitewater affair, in which the Clintons are alleged to have been involved in a property transaction in partnership with the owner of a bank that later collapsed. She will have to respond, alone, without her lawyer, to questions from Starr and the jury. But the hearing is secret; it's a crime even to approach a grand juror.
Exactly what Mrs Clinton may have done wrong is unclear. Maybe, as she insists, she is guilty of nothing. But in the mist of foggy mirrors that is the Whitewater affair, that is scarcely the point. What is more interesting is that a woman so brimming with political savvy has made such a hash of handling the affair. That shambolic record culminated in the latest absurdity, when documents sought by investigators for two years, billings of her legal work in the 1980s, turned up in a box in a workroom used every day in the White House family quarters.
As much as her husband, Hillary Clinton is fodder for armchair psychologists. "Saint or Sinner?" asked Newsweek in a recent cover story, wondering which was the real Hillary: the tireless promoter of women's and children's causes who wrote a book on motherhood and children; or Washington's own Lady Macbeth? Is she a virtuous doer of good works, a First Lady with the courage to go to Peking and condemn China for human rights abuses; or the greedy babyboomer who used her contacts to make an insider's killing in cattle futures trading? The idealistic young Congressional staffer who pursued Nixon over Watergate - or a villain engaged in a Nixonian cover-up of her own? Quite possibly, the answer is all of the above.
First in her year at Yale Law School, she is intellectually at least her husband's equal. In Arkansas, she was as instrumental as he in the education reforms that are his main legacy as Governor. In 1992 her role was crucial: never more so than during the Gennifer Flowers affair, when she dominated a joint TV appearance that perhaps saved the campaign.
In the White House she has been no less a driving force. Unlike other First Ladies, who have rarely strayed from the residential and ceremonial East Wing, she took an office in the cramped, bustling West Wing from which America is governed. Senior policymakers walked in dread of her. Hillary was entrusted with preparing health-care reform. She also did much to shape the deficit cutting package that is the main economic achievement of the first Clinton term.
In retrospect, the spring of 1993 was her apogee - the very moment, it now emerges, she was manoeuvring to bring about the shameful (though perfectly legal) sacking of the White House travel office staff. It was alleged they had mismanaged funds; their defenders say they were victims of a vendetta by the Clintons.
That 23 May, Hillary attained media canonisation, pictured on the cover of the New York Times magazine in an outfit of virginal white. "Saint Hillary", the article was headlined, "More preacher than politician, the First Lady seeks a new Reformation". The descent to earth was swift. Two months later Vince Foster, the deputy White House counsel, committed suicide, in part from depression at the travel office debacle and the deepening controversy over Whitewater. Foster had been a fellow partner at the Rose law firm in Little Rock, and at the White House keeper of Hillary's private legal affairs (including, Ms Clinton's accusers insist, those papers so mysteriously rediscovered this month).
Some say they had been lovers. Asked by ABC's Barbara Walters if that were so, Mrs Clinton did not answer directly - only heightening the belief that the key to the riddle of Mrs Clinton's behaviour over Whitewater may lie in her relationship with Mr Foster.
Shortly after Foster's death details emerged of a $100,000 speculation on cattle futures by a woman so fond of lambasting the Republicans' "Politics of Greed" during the 1980s. Then her health plan failed ignominiously in Congress: that cemented her reputation as an arrogant proponent of Big Government Knows Best. Briefly she retired from the limelight, though her influence on her husband is undiminished. For the American public meanwhile, she is a more divisive figure than ever.
The country is yet to come to terms with a First Lady whose like it has never seen, a career woman who could have been a Cabinet member in her own right. Famously, Hillary Clinton is not a baker of cookies, nor a meek little woman who just "stands by her man," but one who, say the gossips, has been known in the White House to hurl tablelamps, no less, at that man of hers. Only adding to the bafflement are the hairstyles, changing as frequently as her perceived persona.
Right now, that persona is not flattering: for the first time her approval ratings have dropped below 50 per cent. In public she isunbowed by the controversy over Whitewater. Privately, however, she talks of her pain and bewilderment at the criticism she has attracted.
Most important, just like her husband, Hillary Clinton should never be written off. This time, runs the conventional wisdom, Bill will have to defend Hillary. Her peccadilloes, not his, will be the campaign liability of 1996. But don't bet on it. Where was she yesterday, for instance, on the eve of her grand jury appearance? Not in the White House, polishing her story for the interrogation - but in New Hampshire stumping for the President.