The 2011 TIME 100

When Hillary Clinton became Secretary of State, she pledged a "smart power" policy that meant striking up a close working relationship with Secretary of Defense Robert Gates while reshaping the State Department to emphasize development and people-powered diplomacy. She deployed her personal star power in direct contacts with the public overseas, speaking clearly about human rights and freedom of expression on the Internet.

She's been tough too. When China was overassertive about the South China Sea last year, she rallied other nations; when Libya's Muammar Gaddafi threatened to massacre civilians in Benghazi, she was key in building support in the U.N. for the multilateral military action that is helping to protect those civilians. She has strengthened American alliances in Europe and Asia while also engaging the emerging powers of China, India and Brazil.

But above all, Hillary, 63, has set a model of how to be a member of a team of rivals. Unlike in many Administrations that have suffered from friction between State, Defense and the White House, Barack Obama's strongest rival in 2008 has become one of the most effective and loyal supporters in an Administration that has been notably cohesive on foreign policy.

Nye is the author of The Future of Power and a dean emeritus of the Kennedy School