When the private musings of the faceless White House staffer were leaked (i.e. "Who cares what McCain thinks!? He's gonna die soon.), Megan McCain was incensed and said, paraphrasing, " Just who do you think you are? You're a nobody. No one will remember you when you're gone, and people will be remembering my father for hundreds of years!"
I think they both believe that. Sadly, that's likely what matters to them.
Even more sadly, no one but scholars of political minutiae will remember Mr. Mc Cain in 50 years, let alone hundreds.