Sarah Palin is a polarizing individual. Yes, she can connect with the right and much of the center, but that's about all. She's compassionate and would make a great vice-principal. NOTHING MORE.
She completely screwed up every important interview she gave to the left-wing press. As a politician, you can refuse an interview, or demand that the questions be provided in advance. I don't see why she failed to do this, because she came across as woefully ignorant and was unable to answer even basic foreign and campaign policy questions with anything more than inspirational folk-speak.
Biden is not a smart guy - he was selected because he's the UAW's [censored] and Obama wanted to ensure their votes. The Obama campaign strictly controlled what Biden could say, and limited his gaffes. That having been said, Biden is an outgoing guy, like Bush, although less intelligent. Palin is more along the lines of a clueless soccer mom susceptible to moral panic.
Obama and Bush were both intelligent people. Bush may have made comical mistakes, but was not clueless. Obama is at least smart enough to use a teleprompter to overcome his deficiencies in extemporaneous speech.
Palin's resignation will be a disaster to any future campaign she chooses to run. She will either be accused of having screwed something up and resigned to escape punishment, or abandoning the people of Alaska to chase personal ambition. I suspect, and I think this will come out soon, that she resigned for one of two possible reasons:
1. She completely screwed something up.
2. The former mayor of Wasilla got a taste for Neiman Marcus clothing and private jets and has decided to ditch Alaska and move to the mainland where she's been offered a high paying job as a conservative talking head.
