Her debut on the national stage in the early 1990s was a defining era for Clinton, a period when she emerged as Bill Clinton's most influential campaign strategist and policy advisor. She was forceful and methodical in shaping the Clinton administration's domestic policies and political strategy, and proved to be a disciplined partner to her famously disorganized husband: commanding, opinionated, daunting.
"Bill talked about social change, I embodied it," Clinton wrote in "Living History," her autobiography.
Meetings were her milieu. She would arrive toting the crisp yellow legal pads she had carried habitually since her days as a corporate lawyer. Armed with an exhaustively researched grasp of the issues at hand, she would press for still more options while lacerating opposing arguments with surgical precision.
Clinton's all-access pass into the West Wing gave her an intimate education in presidential decision-making that none of her opponents can claim. She observed at close range how big government works, and she learned painfully from her missteps how easily it bogs down.
Yet Clinton has never exercised ultimate executive authority. Unlike some of her campaign rivals, she has no experience in managing massive state budgets or city bureaucracies, a critique pointedly raised by former New York Mayor Rudolph W. Giuliani.
The healthcare initiative started out as Clinton's most ambitious experiment in policymaking and ended up as her greatest management failure, trailing criticism that her performance was flawed by hubris, inflexibility and a penchant for secrecy and political combat.
On the campaign trail, Clinton has offered her assurances that the scars left from her healthcare experience came with lessons learned. Her tight-knit New York Senate office, disciplined campaigns and studied effort to win over legislative colleagues are all evidence, her partisans say, of how she would run her own shop differently in the White House.
But her gates-drawn stance raised concerns that shadow her presidential bid today -- that she reacts with a siege mentality under pressure, retreating behind a restrictive wall of presidential and attorney privilege.
"There's no question that her first instinct was to protect herself and the president," said former Clinton chief of staff Leon E. Panetta.
Presidential historian James McGregor Burns, who studied the uneasy dynamics of the Clinton White House, said that even her setbacks amounted to "educational failures" that toughened her for the long run.
"She's been tested over and over again," Burns said. "The question for voters is whether they feel she passed those tests and whether they think she learned from them."
She'd had some practice
Hillary Clinton's emergence as a key advisor in her husband's 1991 presidential run was hardly sudden. She had worked as a field organizer in Texas during George S. McGovern's defeat in 1972 and in Indiana in 1976 as part of Jimmy Carter's winning campaign.
Clinton also had limited management experience -- as a Wal-Mart director and as board chairman at the activist Children's Defense League, where her successor, Donna E. Shalala -- later a Clinton administration Health secretary -- recalled her as a "natural leader. She took on the same kinds of problems that corporate executives deal with."
From the start, Clinton's campaign role was left as amorphous as possible, allowing her to carve out her own domain.
"No one raised a question about how her role was defined," recalled lawyer Mickey Kantor, the campaign chairman. "It was assumed. You wanted her involved at the highest level."
Involved she was, and in everything. She used her ties to New York legal circles to raise cash and tap political pros. While staffers took a breather on a bus caravan through Texas, old friend Bill Burton watched as "Hillary sat in the back and took charge of a press release on natural-gas policy." As she peppered her husband's aides with strategy, she was empire-building -- cherry-picking loyalists who would work at the core of her White House staff.
Kantor and other campaign veterans credit her as the driving force behind the rapid-response "war room" operation. Later, she rode herd on the "defense team," a cloistered group of staffers and lawyers who fended off media queries about the couple's financial deals, rumors of Bill's infidelity and his youthful dealings with Arkansas draft officials during the Vietnam War.