This is an excellent article in The New Yorker by Ryan Lizza. A few excerpts:
Biden agreed to let Obama’s campaign team consider him, but with a caveat: “I wanted to make sure we understood each other—that, even if I vetted and he wanted me to take the job, I wasn’t committing to do that. When the time was appropriate for him, if I was the guy, I needed to spend at least two or three hours with him to understand what the role would be.” Biden wanted what amounted to an oral contract between him and Obama, spelling out his specific responsibilities in an Obama White House...
Obama also asked Biden whether he thought that he was more suited to a different position. “He said, ‘You have a great interest in national-security policy, foreign policy,’ ” Biden told me. “He wasn’t offering me this, but he said, ‘Would you rather be Secretary of State instead of Vice-President?’ And I thought a lot about that.”
During the primaries, Biden often played the role of policy grownup, the candidate who liked to chide the unrealistic plans of his rivals. According to a senior Biden aide, after a debate in which Bill Richardson, the New Mexico governor, argued that he could have all hundred and sixty thousand American troops out of Iraq in a matter of months—something that is logistically beyond reach, according to most observers—Biden approached Richardson backstage and told him that the plan was impossible. Richardson didn’t seem concerned. “I know it is,” he said. (A spokesman for the Governor said that Richardson does not recall the exchange.) In an Obama White House, Biden wants to be just as direct.
42 minutes ago