Behind a demure image lay utter political ruthlessness
Nancy was the driving force behind her husband's bid to become the US president
Nancy Reagan, the former first lady of the United States, arguably exercised more power than any other president's wife.
Operating under a public cover of wifely submission, she was the crucial influence over her husband's entire political career.
"If Ronald Reagan had married Nancy the first time round," James Stewart once remarked, "she could have got him an Academy Award."
As a politician, Reagan's appeal was that of an easy-going, uncomplicated, nice guy, whose forte was to bring common sense to bear upon the intractable problems of state. The image proved extraordinarily successful because in large measure it was based upon the truth.
But nice guys, by definition, do not possess the ruthlessness and drive required to secure the presidency. Nancy Reagan provided the intensity of purpose that clinched success.
Her determination to see her husband on the pinnacle of power had grown out of the insecurities of her youth and was pursued with a deadly combination of wariness and suspicion.
"Ronald Reagan trusts everyone and likes everyone," explained Nancy Reynolds, who handled public relations for the Reagans. "Nancy has a more discriminating antenna about people. She's seldom wrong. And if she feels someone is hurting him she'll speak out.
"She's a tiger at such moments, and thank God for it, because her husband never says No. She makes sure the sharks are kept at bay."
Similarly, on the campaign trail, she made quite sure that Reagan's aides were kept up to the mark. In the White House - particularly during the president's second term, when his faculties were clearly on the wane - her hostility meant political death and her penchant for firing people earned her the nickname of "Little Gun".
Her performance as first lady raised eyebrows. In private, she would hold her staff at bay with frozen stares; in public, she would fix her husband with a gaze of rapt, not to say imbecilic adoration.
Her devotion remained constant. "My life began when I married Ronnie," she said, "I think I would have died if I hadn't married him. He is my hero."
The sceptical remained unconvinced. They were also inclined to doubt the genuineness of Nancy Reagan's commitment to social causes.
They knew that she loved expensive clothes (and especially those that designers made for her gratis); and that she instinctively preferred the company of the super-rich.
As soon as she entered the White House, she carried out extensive redecoration and ordered a set of china costing over $200,000 - this at a time when the president was stressing the importance of restricting expenditure.
She never succeeded in creating a compassionate image.
She was born Anne Frances Robbins in New York on July 6, 1921. Her father, Kenneth Seymour Robbins was an insurance salesman, albeit from an old New England family. Her mother (née Edith Luckett) pursued a rackety theatrical career independently of her husband.
By the time Nancy was two, her parents' marriage was virtually over. She was parked with a maternal aunt; in the summer she would visit her father in New Jersey.
Her parents divorced in 1928 and Kenneth Robbins remarried.
In 1929, her mother married Loyal Davis, an austere and forbidding Chicago neurosurgeon of tightlaced, unforgiving Republican views.
In 1938, Nancy Robbins was adopted by her stepfather and thereafter featured as Nancy Davis, making no effort to see her real father. The next year, she went to Smith College, where she continued to dabble in drama, then pursued an acting career.
Her mother knew Spencer Tracy, who managed to fix her up with a date with Clark Gable. Tracy also obtained a screen test for her at MGM and in March 1949 she signed a contract with that studio at $300 a week.
It was in 1949 that Nancy Davis first met Ronald Reagan, whose movie career was already in decline, but who had become president of the Screen Actors Guild.
Reagan had been previously married to the actress Jane Wyman, with whom he had two children.
Nancy Reagan recalled that she had known "right away" that Ronald was the man she wanted to marry.
Reagan, though, was involved with several other women and it was only after Nancy Davis became pregnant that, in March 1952, he married her. Their daughter Patti was born that October.
Meanwhile, Nancy Davis's career had been foundering.
Ronald Reagan's career was also at a low ebb in 1952, though he would be saved two years later by a lucrative contract to introduce General Electric Theatre on television.
By the time that their son Ronald 'Skipper' Reagan was born in 1958, the Reagans were becoming more closely involved with politics.
Though he campaigned as a Democrat for Nixon in 1960, he became a Republican - and a right-wing one - soon after John Kennedy's victory. Four years later, Reagan was the one bright spot in Barry Goldwater's presidential campaign.
Nancy Reagan was certainly behind her husband's decision to run for Governor of California in 1966. He won.
It was certainly difficult to strike a human spark from her in interviews. "She just drove me nuts," complained a journalist, Nancy Collins. "She just sits there with her legs glued together, her hands all white knuckles, teeth grinding and that face just a mask - no animation, no laughter, no spontaneity, nothing. She was awful, just awful."
Reagan made a cursory attempt at the US presidency in 1968, but was re-elected as governor in 1970, albeit with a reduced majority.
Nancy proved a formidable force in Reagan's campaign in 1976 to wrest the Republican nomination from President Ford and failure stimulated rather than quenched her ambition.
With the failures of Jimmy Carter's presidency, the Reagans enjoyed a relatively smooth passage to the presidency in 1980.
They had two children. Patricia ('Patti') decided in the 1960s that drug-taking and wild living were likely means to self-fulfillment and later changed her name to Patti Davis.
The younger, Ronnie, or 'Skipper', became a ballet star and later a TV host.
In later life, Ronald Reagan suffered from Alzheimer's disease and died in 2004. During a seven-day state funeral, Nancy Reagan led America in mourning and at a sunset memorial service kissed her husband's coffin and mouthed the words: "I love you."
As she became increasingly frail, she withdrew from the public eye. Nancy Reagan is survived by her son and daughter and a stepson from her husband's first marriage.
Nancy Reagan, born July 6, 1921, died March 6, 2016.