Obama, without a doubt, has shifted the conversation.
McCain alas says that 16 months is a good timetable for withdrawal but it has to be based on the conditions on the ground.
And so, this is the key differentiator between Bush McCain and Obama: Obama has said that as president, he would set the strategy and the generals on the ground would support it.
With Bush McCain, the generals on the ground have dictated the strategy because Bush hasn't had the fortitude to lead.
But now it seems everyone agrees.