The problem with Biden is not substantive. He seems intelligent, if not exceptionally so. He is quite affable, sensible in his policy prescriptions, and on paper complements Obama nicely. He brings foreign policy gravitas to the campaign, and in general, experience. His sins are his candor and verbosity. The former is refreshing and is actually consonant with the general "change" theme of the Obama campaign. The latter, his verbosity, or really a propensity towards verbal diarrhea, is what is potentially toxic in the modern campaign. In his own campaign for president, which unfortunately never gained traction, he seemed to tame his tendency to put his foot in his mouth.
I hasten to add, my observation and the core of my criticism is exceedingly shallow. But alas, so are presidential campaigns and their media coverage.