Lanky and lean in a charcoal suit, Samantha Power, 37, zooms through the halls of Harvard's Kennedy School of Government with the kind of purposeful gait you think only exists on Aaron Sorkin shows. She's tailed by speed-walking grad students offering their most erudite thoughts on human rights: "Karzai. Afghanistan. Genocide. Read this!" says one guy, huffing. She grabs his printouts. "Thank you," she tells him, then leaves him in the dust. "That guy's not even in my class," she says.

There's good reason to follow Power. After cutting her teeth as a war correspondent in the former Yugoslavia, she founded a major center for the study of human-rights policy at Harvard, won the Pulitzer for A Problem From Hell (her 2002 book about genocide), and, last year, signed on with the Barack Obama campaign as a foreign-policy adviser. She juggles this role with her Harvard teaching responsibilities and regular speaking engagements. On a recent evening, she addressed future leaders of developing nations that had been singled out by the World Economic Forum. Swigging beer at the podium, Power spoke brilliantly and totally off-the-cuff about "systematic rape," "components of influence," and "crises of legitimacy."

But even in the face of atrocities, Power maintains a "glass-half-full approach to the human condition." It's evident in her new book, Chasing the Flame: Sergio Vieira de Mello and the Fight to Save the World, a masterful biography of the U.N. High Commissioner for Human Rights who was killed by a truck bomb in Iraq in 2003. "Brokenness is the operative issue of our time — broken souls, broken hearts, broken places," says Power. "I don't know any figure who bumped up against brokenness like Sergio did" — and yet he held an unflagging belief that he could effect change. In Cambodia, he helped repatriate over 300,000 displaced people, and he brought over 500,000 Rwandans home from refugee camps. It's no surprise Terry George, director of Hotel Rwanda, is already writing the screenplay.

Eye on the world:

But of all her projects, Power gets the greatest satisfaction from working with Obama, whom she calls "the most exciting person in political life." After all, an Obama presidency could bring Power to Washington to help formulate our foreign policy. National Security Advisor? Secretary of State? "If he wanted me to do something," she says, "it would be impossible not to." At press time, Obama's fate was uncertain but Power's wasn't — don't take your eyes off her.

What Do You Think?