Karma on Biden
This is a good diary arguing in support the choice of Biden for VP. Karma for All points out that Barak Obama has already made clear that his criteria for his VP choice included someone who would disagree with him and challenge him. As I've argued elsewhere, this is a central characteristic of success, looking for evidence and arguments that challenge your existing conclusions. In short McCain, and the press, will frame this as a negative on Obama. The counter argument is that Biden will provide critical review, an essential element to a success.