Why Barack Obama Is Winning

General David Petraeus deployed overwhelming force when he briefed Barack Obama and two other Senators in Baghdad last July. He knew Obama favored a 16-month timetable for the withdrawal of most U.S. troops from Iraq, and he wanted to make the strongest possible case against it. And so, after he had presented an array of maps and charts and PowerPoint slides describing the current situation on the ground in great detail, Petraeus closed with a vigorous plea for "maximum flexibility" going forward.

Obama had a choice at that moment. He could thank Petraeus for the briefing and promise to take his views "under advisement." Or he could tell Petraeus what he really thought, a potentially contentious course of action — especially with a general not used to being confronted. Obama chose to speak his mind. "You know, if I were in your shoes, I would be making the exact same argument," he began. "Your job is to succeed in Iraq on as favorable terms as we can get. But my job as a potential Commander in Chief is to view your counsel and interests through the prism of our overall national security." Obama talked about the deteriorating situation in Afghanistan, the financial costs of the occupation of Iraq, the stress it was putting on the military.

A "spirited" conversation ensued, one person who was in the room told me. "It wasn't a perfunctory recitation of talking points. They were arguing their respective positions, in a respectful way." The other two Senators — Chuck Hagel and Jack Reed — told Petraeus they agreed with Obama. According to both Obama and Petraeus, the meeting — which lasted twice as long as the usual congressional briefing — ended agreeably. Petraeus said he understood that Obama's perspective was, necessarily, going to be more strategic. Obama said that the timetable obviously would have to be flexible. But the Senator from Illinois had laid down his marker: if elected President, he would be in charge. Unlike George W. Bush, who had given Petraeus complete authority over the war — an unprecedented abdication of presidential responsibility (and unlike John McCain, whose hero worship of Petraeus bordered on the unseemly) — Obama would insist on a rigorous chain of command.

Barack Obama has prospered in this presidential campaign because of the steadiness of his temperament and the judicious quality of his decision-making. They are his best-known qualities. The most important decision he has made — the selection of a running mate — was done carefully, with an exhaustive attention to detail and contemplation of all the possible angles. Two months later, as John McCain's peremptory selection of Governor Sarah Palin has come to seem a liability, it could be argued that Obama's quiet selection of Joe Biden defined the public's choice in the general-election campaign. But not every decision can be made so carefully. There are a thousand instinctive, instantaneous decisions that a presidential candidate has to make in the course of a campaign — like whether to speak his mind to a General Petraeus — and this has been a more difficult journey for Obama, since he's far more comfortable when he's able to think things through. "He has learned to trust his gut," an Obama adviser told me. "He wasn't so confident in his instincts last year. It's been the biggest change I've seen in him."

(See photos of Obama's extended family here.)

(See a gallery of campaign gaffes here.)