Obama's keeper: Valerie Jarrett:

You may not recognise her face, or her name. Yet Valerie Jarrett is arguably the most powerful person in the White House apart from the President. Robert Draper meets her

On 25 January 2008, the day before the South Carolina Democratic primary, Barack Obama endured a gruelling succession of campaign events across the state. When his staff informed him the evening would conclude with a brief show-up at the Pink Ice Ball, a gala for the African-American sorority Alpha Kappa Alpha, Obama flatly refused to attend. "We're not gonna change anybody's mind," he said.

Rick Wade, a senior adviser, Stacey Brayboy, the state campaign manager, and Anton Gunn, the state political director, took turns to beseech their boss. The gala, they told Obama, would be attended by more than 2,000 college-educated African-American women, a constituent group that was originally sceptical of the candidate's "blackness". They would be in and out in five minutes. Obama's irritation grew. "Man, it's late, I'm tired," he snapped. The three knew what their only option was at this point. "If you want him to do something," Gunn would later tell me, "there are two people he's not going to say no to: Valerie Jarrett and Michelle Obama."

At the day's penultimate event, a rally in Columbia, Gunn, Brayboy and Wade pleaded their case to Jarrett, the Obamas' long-time friend and consigliere. Jarrett informed Michelle of the situation and when the candidate stepped offstage from the rally, Obama's wife told him he had one last stop to make before they called it a night.

"I told Anton I'm not going to any Pink Ice Ball!" Obama barked. Then Jarrett glided over to the fuming candidate. Her voice was very quiet and very direct.

"Barack," she insisted, "you want to win, don't you?"

Scowling, Obama affirmed that he did.

"Well then. You need to go to Pink Ice."

"And he shuts up," Gunn recalls, "and gets on the bus."

Among the narrative threads that are weaved, almost uninterrupted, throughout the history of the American presidency, is the inevitable presence in the White House of The One Who Gets the Boss. Karen Hughes got George W Bush. Bruce Lindsey got Bill Clinton. And so on, back to Thomas Jefferson's lifelong reliance on the counsel of James Madison.

Valerie Jarrett is a Washington outsider with a Washingtonian's mind-deadening job title: senior adviser and assistant to the President for intergovernmental affairs and public engagement. Roughly translated, she is Obama's intermediary to the outside world. But the 52-year-old Jarrett is also the President's closest friend in the White House, and it is not lost on her colleagues that when senior staff meetings in the Oval Office break up, she often stays behind with the boss.

Over a four-month period of reporting, I struggled to understand Jarrett's ineffable raison d'être in the Obama White House. Perhaps proving that nothing succeeds like failure, my plaintive queries were unexpectedly rewarded one afternoon by a telephone call from the President himself.

"Well, Valerie is one of my oldest friends," Obama began. "Over time, I think our relationship evolved to the point where she's like a sibling to me ... I trust her completely." As his surrogate, Jarrett is trusted "to speak for me, particularly when we're dealing with delicate issues".

After our conversation, I began to reflect on Jarrett's portfolio. Broadly speaking, it consists of "outreach" – endless meetings, conferences and speeches. She functions as Obama's de facto conduit to the business community. Among the President's economic team, only Jarrett, the former president of a Chicago real estate development firm, has actually run a multimillion-dollar business. Her street cred with the private sector is an obvious asset to a president confronting a major recession.

Jarrett also serves as the White House's unofficial champion of minority issues. This may seem superfluous, given that a black man inhabits the Oval Office – until it's noted that Obama's inner circle consists largely of white males, same as it ever was.

Jarrett's shared experience with Obama is about race – and on a deeper level, about the coexistence, in the post-King African-American psyche, of conscience and ambition, activism and accommodation. Their identity rests on that fulcrum; it is, as Barack Obama would say, who they are.

Authenticity has a lot to do with place, of course. The Obamas and Valerie Jarrett experienced first-hand the hard-won progress of a Chicago beset with racial and class divisions during the administrations of Harold Washington, who was the city's first black mayor, and Richard M Daley. "There was a certain sense we all shared that people can change, communities can change, cities can change," Jarrett said when I asked her to talk about what Chicago means to her and the Obamas.

Still, she told me, what Chicago provided Obama with most of all was family – beginning, of course, with Michelle Robinson. "My guess is that Michelle's childhood was his idea of perfection," Jarrett said. "It allowed him to anchor himself with her and with her family. To me, that's the most special thing about Chicago for him." It didn't take long for Jarrett to become part of Obama's patchwork family. As Daley's deputy chief of staff, Jarrett was already one of the city's power brokers in 1991 when her friend and co-worker, Susan Sher, suggested that she take a look at the resumé of a promising young African-American lawyer named Michelle Robinson. The applicant made an impression on Jarrett and vice versa.

In less than a year, Michelle's fiancé began to confide in Valerie Jarrett. He showed her pages from a book he was writing. That book, Dreams From My Father, explored Barack Obama's inner struggle. "He talked about how hard it was – things he hadn't dealt with yet," she recalled. "'It isn't just a matter of writing a simple story,' I told him. 'You've got to deal with the fact that your father left you at a very young age. And you lived in a variety of different settings at an age where it could've been discombobulating. Your grandparents are white and you look black. Your friends in Hawaii all are different-looking and that's great – but you come to the mainland, and things are much more black and white, literally.'"

***

Jarrett was born of African-American parents in Shiraz, Iran, where her physician father was running a hospital as part of an American aid programme. Obama's fabled "exoticism" was therefore comprehensible to her, the President told me. "She and I both are constantly looking for links and bridges between cultures and peoples," he said.

Obama, as his memoir would reveal, sought connection to the heroes of the civil rights movement. Jarrett's struggle had been of a different sort: how to measure up to the role models that filled her life. Her father, Dr James Bowman, was an eminent pathologist. Equally influential was her mother, Barbara, a childhood-development expert.

The fast track laid out for Valerie Bowman – a Massachusetts boarding school, then Stanford, then a law degree at Michigan, then marriage and work at a corporate law firm – was one she pursued with neither resistance nor zeal, "kind of like an automaton", she told me.

Eventually she quit both her marriage and her job, and in 1987, as the mother of a two- year-old daughter, she went to work for Mayor Washington's corporation counsel, Chicago's chief legal officer handling civil claims.

Over the next 15 years, her upward trajectory would outpace even Obama's. Jarrett's unhappy years as a real estate lawyer now paid off in a city law department responsible for maintaining Chicago's business base. Washington died of a heart attack in 1987, but her work ethic and supple intelligence distinguished Jarrett in the eyes of Richard M Daley, who took office two years later. The new mayor promoted her to deputy chief of staff – and later to the post of planning commissioner, thereby baptising Jarrett in the racially-charged torrent of urban affairs.

From 1991 until 1995, she presided over a rancorous but largely-successful makeover of the city's landscape. Meanwhile, she was raising her daughter and developing a social life that revolved around an intimate community of like-minded black urban professionals who, like Jarrett, sought advancement not only for themselves but for the local African-American community. Chief among them were the Obamas. Jarrett brought Michelle into the Daley administration, attended their wedding, threw a book-signing party for the Dreams From My Father author and generally assumed a big-sisterly presence in the young couple's lives such that "I don't think either of them made major decisions without talking to her", according to Susan Sher.

As Obama told me: "We've seen each other through ups and downs." For Jarrett, one such low point came in 1995, when she began to lose the mayor's support. Wounded, Jarrett bolted for the property development firm Habitat – only to have Daley ask her to keep a foot in the public sector by offering her the post of chairwoman at the Chicago Transit Board. She accepted. Soon other boards beckoned, including the University of Chicago Medical Center and the Chicago Stock Exchange. Habitat made her an executive vice president. By 2002, it was as if the city had awakened one morning to find that Valerie Jarrett had taken over.

Over the ensuing five years, the role Jarrett played in Obama's political ascent was important but also confined. For his senatorial campaign, she made key introductions to the donor community. She was among the handful of close advisers who met at the close of 2006 to carry on a rolling discussion of the risks entailed in a presidential run. And during the first six months of Obama's presidential campaign, Jarrett remained in constant contact with him but otherwise stayed in Chicago to run Habitat – she had become chief executive in January – and the Chicago Stock Exchange.

That arrangement began to change on the evening of July 17 2007, when Obama convened a meeting at Jarrett's Chicago town house. The presidential campaign was not gaining traction in the national polls. "Lots of things were bubbling up, and no one was really handling issues that would arise, either in Chicago (at headquarters) or on the road," says Penny Pritzker, who was one of the meeting's participants and the finance chairwoman of the campaign. "You needed another smart, capable, really close adviser involved who could play a bridging role. Valerie was the perfect solution."

Not everyone agrees with Pritzker. She never actually moved into headquarters, "and that was good and that was bad", says the White House senior adviser, Pete Rouse, who at that time was Senator Obama's chief of staff. Jarrett's ambiguous role particularly annoyed the campaign manager, David Plouffe. Jarrett and Plouffe tangled over issues ranging from where the campaign should be spending its money to where the candidate should be spending his time.

Today Plouffe offers unqualified praise for Jarrett's work as a campaign surrogate but says, "She wasn't terribly involved in strategic issues." This is probably true – but only because the campaign did not consider the matter of race to be a "strategic issue". On this subject, Jarrett consistently and forcibly weighed in.

It was Jarrett, several aides say, who helped convince otherwise sceptical senior staff that Michelle Obama should go to South Carolina in November 2007 and give a speech addressing fears in the African-American community that harm might come to the black candidate. It was Jarrett who strongly encouraged Barack Obama to give his race speech. Numerous campaign officials credit Jarrett, along with the communications director Anita Dunn and Stephanie Cutter, Michelle Obama's chief of staff, for helping to rehabilitate Mrs Obama's "angry black woman" image.

A few days after the election, the president-elect told his new chief of staff Rahm Emanuel: "I want her inside the White House."

When the subject is Valerie Jarrett, it's fair to say that Emanuel's words fall short of effusive. Their opposing qualities – deliberateness and sensitivity in Jarrett; speed and brutal practicality in Emanuel – may reside harmonically in Barack Obama. But what the two aides represent isn't simply a function of velocity or decibel level. While both of them obviously want the President to succeed, Emanuel's criteria for "success" are straightforward. Jarrett, according to Cecilia Munoz, Jarrett's director of intergovernmental affairs, is "very focused on why he ran in the first place" – a psychological calculation that only Jarrett would presume to undertake and which therefore is bound to drive others nuts.

***

"Where's my picture?" Valerie Jarrett exclaimed, addressing no one in particular. She stood up from the conference-room table in her office and walked over to the bookshelf. "They brought these to me today."

The image was odd. It featured five figures seated on the couches and chairs of the Oval Office: the President; Jarrett; the Reverend Al Sharpton; the former Republican House speaker, Newt Gingrich; and the New York mayor, Michael Bloomberg. Standing over me, Jarrett said: "I love that photo."

That unlikely meeting had been arranged by Jarrett. Sharpton, Gingrich and Bloomberg were part of a group convening in Washington to commemorate the 55th anniversary of the landmark Brown v Board of Education school desegregation decision by promulgating education as a civil right.

"I liked the idea of getting this odd quartet together to come around an issue," Jarrett told me. "Because it would show the American people that this is what the President is about, getting unlikely combinations together."

I asked: "If you hadn't suggested that this meeting take place, do you think anyone else would have suggested it?"

Jarrett looked across the table at her friend, the White House communications director, Anita Dunn, who had dropped in on the interview. Dunn stopped taking notes and flashed Jarrett a look of abiding doubt.

"Probably not," Jarrett then murmured.

"Probably not?" exclaimed Dunn, who had been virtually silent until now. "Absolutely not!"

Dunn's outburst was delivered with a depth of appreciation that I had not picked up on elsewhere in the West Wing. Though Dunn is white, her words reminded me of the interviews I conducted with several African-Americans who had served at high levels in the Obama campaign. To them, Valerie Jarrett was something of a heroine.

Without Jarrett, these officials said they believed, their opinions and the often-legitimate concerns voiced by black leaders like Sharpton would have been thoroughly disregarded by the white-dominated senior staff. "There's a cultural nuance that they just didn't get," one such African-American staff member told me. "And the landscape of our campaign is littered with hundreds of stories where she intervened and voices got heard and decisions got made that might've gone a different way."

As to just how much difference Valerie Jarrett's various interventions had made, the staff member admitted he couldn't say. It wasn't for him to judge, anyway. That was between Obama and Jarrett.