I hate to say it, but along with having a complicit media, the Bidens seem to have more effective handlers for this sort of thing than the Palins do.
Because the Biden’s have been in the business longer. You don’t get caught plagiarizing papers in law school, quoting others without citing them when you run for president in the 80’s, have brain surgery for a tumor but never get asked to see the subsequent CT and MRI scans (to see how much brain is left, if any) and become VP without good handlers. No, say what you want about Crazy Joe, he sure knows how to play the game.