Caputo said Clinton, 60, and Williams, 53, treat each other more as peers. By contrast, Clinton's former campaign manager, Patti Solis Doyle, while equally trusted, is 42 and had related to her boss more as an employee than as an equal.
"Maggie's relationship goes back 25-plus years. Patti's goes back 15," Caputo said, adding, "Maggie has dealt longer on a national stage."
Williams was born and raised in Kansas City, Mo. Although a Baptist, she came to Washington to attend Trinity College, a Catholic women's college, from which she graduated in 1977.
Along the way, she shed her given name, Margaret, becoming known universally as Maggie.
After college she worked in the press office of the Democratic National Committee and for Rep. Robert Torricelli (D-N.J.) before landing the job at the Children's Defense Fund.
At the White House, Williams was the highest-ranking African American, and she became an integral part of the Clinton inner circle. The mere fact that she attended Panetta's high-level meetings was unprecedented. Hillary Clinton was the first presidential spouse to have an office in the West Wing, and she installed Williams next door with a dual title as "assistant to the president."
But -- by design -- Williams was little-known outside the White House. That frustrates friends who believe she has deserved more credit and recognition.
"No matter what position she has had -- and she has had a lot of powerful jobs -- she never steps forward when the pictures are being taken," said a close friend and former colleague who spoke on condition of anonymity because Williams asked her friends not to talk to reporters about her.
"That's maddening to me and a lot of other people who know her."
Williams did not respond to a request for an interview.
Passionate, persistent
Friends say her self-deprecating manner allows her to focus those around her on the task at hand and the principles at stake. She is passionate and persistent and -- rare for someone in politics -- not egocentric. And that's one reason she inspires others.
One friend tells a story from her time at the Children's Defense Fund when the nonprofit was trying to start a public service ad campaign to discourage teenage pregnancy. Williams tried to persuade a cutting-edge advertising firm to work for free.
