If Elected ...

Mr. Obama, who noted that General Petraeus wanted “maximum flexibility” in setting withdrawal schedules, said he “pushed back” when he met with the commander in July by making the case for sending more forces to Afghanistan, which the Democratic candidate views as the main battleground against terrorists.

Mr. McCain, who argued that a favorable outcome in Iraq is vital for American strategy in the Middle East and its overall efforts against terrorists, repeatedly invoked General Petraeus’s counterinsurgency strategy and said he would be inclined to give General Petraeus considerable latitude in setting force levels in Iraq. At the heart of the dispute is Mr. Obama’s 16-month schedule for withdrawing American combat brigades, a timetable that is about twice as fast as that provided for in a draft American and Iraqi accord. Would that deadline spur the Iraqis to overcome their political differences and enable the United States to stabilize Iraq at far lower troop levels, as Mr. Obama asserts?

Or would it tie the hands of commanders and undermine political progress when the security gains in Iraq are still fragile, as Mr. McCain contends?