The world has an ongoing love-hate relationship with America, born often of the higher expectations and disappointed hopes that it holds for the world's most enduring democracy. The United States also has sworn enemies and dangerous rivals. Much has been made of the symbolic impact Mr. Obama's presidency will have on global opinion. But more than his image, it will be his leadership that will define the United States' foreign relations for years to come. Just as America still needs the world, the world still needs America. Its national genius for innovation and historic willingness to advance fearlessly into the unknown, combined with its still unrivaled might, uniquely qualify it to lead the way and serve as a backstop in an age of uncertainty.

Mr. Obama's lack of experience on the national and international stage represents to a certain degree an unknown variable. But anyone watching the campaign he has waged over the past two years has reason to be optimistic about the kind of leadership he will deliver. With a steady and calm temperament, a keen and dynamic intellect, an easy smile and a wisdom and authority that defy his years, Mr. Obama has made his case by appealing to the best and loftiest of what America represents, without stoking the divisions and resentments that threaten the cohesion of our national fabric. It's a fabric that must hold, because only an America united of purpose can mobilize the effort, both at home and abroad, needed to face today's challenges.