Biden's health is bad enough to provide a minimally plausible reason for him to "withdraw." BP (Before Palin), I would have considered this an outlandish thought. Now, I ain't so sure.
Also, how is that The Anointed One was not astute enough to realize that Joe Biden, a high-functioning alcoholic if there ever was one, is not taken seriously anywhere except Delaware, and there only by those who cannot read and write and have no TV? (Perhaps a DE majority?)
One of my favorite statements about Biden at the time was Scott Ott's of Scrappleface:
Sen. Obama, who chose an elderly white man name Joe Biden as his running mate rather than his rival Sen. Hillary Clinton, said he avoided picking Mrs. Clinton “to spare her the humiliation that John McCain plans to impose on Sarah Palin.”