Photo Credit : Thirty30Photography at Flickr.com

Obama sketched out a different theory of social change than the one Clinton had implied earlier in the evening. Instead of relying on a president who fights for those who feel invisible, Obama, in the climactic passage of his speech, described how change bubbles from the bottom-up: “And because that somebody stood up, a few more stood up. And then a few thousand stood up. And then a few million stood up. And standing up, with courage and clear purpose, they somehow managed to change the world!”

For people raised on Jane Jacobs, who emphasized how a spontaneous dynamic order could emerge from thousands of individual decisions, this is a persuasive way of seeing the world. For young people who have grown up on Facebook, YouTube, open-source software and an array of decentralized networks, this is a compelling theory of how change happens.

Clinton had sounded like a traditional executive, as someone who gathers the experts, forges a policy, fights the opposition, bears the burdens of power, negotiates the deal and, in crisis, makes the decision at 3 o’clock in the morning.

But Obama sounded like a cross between a social activist and a flannel-shirted software C.E.O. — as a nonhierarchical, collaborative leader who can inspire autonomous individuals to cooperate for the sake of common concerns.