She's a pit bull, not a parrot
Watching the Gibson interview of Palin, I realized something.... Clearly the R party chose Palin at least partly because she's an independent thinker. Along with the obvious female demographic stuff, she's pleasing to folks who like to reach their own conclusions. This is another part of the West vs East divide that I mentioned earlier.
Westerners have more of a Protestant mindset, Easterners more Catholic. Westerners prefer to start from experience and observation, Easterners prefer to start from Received Authority.
Trouble is, after picking her for this quality, the RNC has put her in a position where she's required to repeat the standard credos and encyclicals of the Bush Dynasty. As the Gibson interview showed, she's not very good at defending things she doesn't really believe.
Hiring a candidate for one quality and then using her for another makes as much sense as hiring a ballerina from the Plumbers section of the phone book.
On the other side, Joe Biden has similar independent qualities. He's famous for saying true and commonsensical things which disagree with the party credo (i.e. he's famous for "gaffes"). But the DNC is not forcing him to be a pure parrot. It's clear that Biden has more room to speak his own mind, more room to attract non-formulaic thinkers.
RNC, as usual, manages to turn a smart move into a dumb one.