Well, as Ambinder notes, after months of Obama saying “he or she” in response to Veep questions, the candidate says “he” very specifically throughout the following answer.
Let me tell you first what I won’t do. I won’t hand over my energy policy to my vice president, without knowing necessarily what he’s doing. I wont have my vice president engineering my foreign policy for me. The buck will stop with me, because I will be the president. My vice president, also by the way my vice president also will be a member of the executive branch, he won’t be one of these 4th branches of government where he thinks he’s above the law.
No mention of “she” anywhere. So unless this is a big head fake, there will be no Hillary, nor Sebelius.
I still think it’s Biden.