Some of her best road stories involve Holbrooke, her close friend, a maestro of diplomacy for more than four decades. (Holbrooke was meeting with Hillary in her office last December when he collapsed and was rushed to the hospital, where he later died from a ruptured aorta.) At his Kennedy Center memorial service, which played more like a roast, she recalled that Holbrooke was once, in Pakistan, so insistent on making a point that he followed her all the way into the ladies’ room. On boarding her plane, he would test every seat to see which was the most comfortable, then hound whichever official was assigned to it to trade with him. Hillary especially enjoyed when he would disappear into the airplane restroom and emerge like an oversize Easter bunny in his bright-yellow sleeping suit. “On hearing Winston Churchill’s motto, ‘Never, never, never, never give up,’ [Richard] called Churchill halfhearted,” she said. Hillary thinks this also perfectly captures her own theory of persistence.

Aloft, the secretary of state can often be found with a black binder clip in her hair instead of fastened onto classified documents. It helps. Her stylist, Isabelle Goetz, does her hair in Washington, but on the road—unless the ambassador’s wife can recommend someone good—she takes care of herself. For years she’s routinely done her own makeup, which is easier because she has good skin. And her genes seem unusually strong. Dorothy Rodham, Hillary’s mother, is 92 but looks more like 80. Hillary is 63 but seems a bit younger. She is one of those lucky people who look better—or at least not worse—with age.

All of this is relevant politically because it means that in 2016, when she’s 68, she is unlikely to be written off as too old to run for president. Since the beginning of the year, Hillary has said repeatedly that she will leave office no later than early 2013 and retire from public life. In Bahrain, just before the Middle East upheaval, I heard her be more direct than ever before on the subject: “I’ve had a fascinating and rewarding public career .... I think I will serve as secretary of state as my last public position and then I’ll probably go back to advocacy work, particularly on behalf of women and children, and probably around the world.”

Hillary isn’t as calculating as her public image. The 2000 Senate race, for instance, was practically serendipitous. But it’s hard to believe “Clinton” and “ambition” have been fully sundered. In 2016, the Democrats are unlikely to have anyone better or more acceptable to different parts of the party. The nearer-term options are far-fetched. When Bob Woodward said on CNN last fall that Hillary’s switching jobs with Joe Biden was “on the table,” the reaction inside both the White House and State Department was to scoff. Neither has an incentive to switch. With the Iraq portfolio already in his pocket, Biden gets plenty of foreign-policy action. His bigger concern is staying on good terms with Hillary. In late 2009, he worried that their long and friendly relationship was in jeopardy over Af-Pak policy. He wanted few troops and heavy reliance on Predator drones; she wanted an open-ended, hugely expensive counter-insurgency commitment. The president ended up sending many more troops than Biden wanted—a total commitment of 100,000—but with withdrawal deadlines beginning this year that Clinton, siding with the Pentagon, opposed. To ease the tensions, Biden and Hillary stepped up their breakfasts and lunches where they call each other “dear.”

Uncommon Ground

Hillary has often said that this is the hardest job she’s ever had. It’s not just the constant travel but also the speed and range of the issues she must master. She finds being secretary of state even more taxing than the 2008 campaign, where she could go on autopilot and give the same speech six times in a day, and had heard all the questions before. “With each month there’s more wear and tear,” says Jake Sullivan, a young lawyer and former Rhodes scholar, who has emerged as one of her closest advisers. “But she also gets more energized and comfortable.” A half-dozen of her friends agree that they have never seen her more in her element. “She seems engaged, happy, focused, determined, and very tired from all the travel,” observes Tom Vilsack, an early supporter from his days as governor of Iowa, who is now the secretary of agriculture. “I can’t remember her ever working this much,” says Dr. Irwin Redlener, who has advised her for many years on children’s issues.