Look for Biden to attack McCain, Bush and the Republicans during the VP debate--but she won't be able to respond adequately (other than motherhood statements) because she doesn't know enough about the issues (iraq, economy) to give out an informed answer.
Joe Biden doesn't have to attack directly Palin--but he will be on offense most of the time. Gov. Palin, OTOH, will be on a defensive crouch, hoping to endure the longest one and a half hour debate of her life.
the best she can do is meet the very low expectations--but it won't be enough.