A new story arc is hard work -- much easier to just use the old one. McCain is another perfect example of this laziness, and it's going to hit Hillary even worse than it has already.
Clowns like Ad Nags have internalized Murphy's Law of Lab Reports -- 'Draw all curves before plotting any data' -- and applied it to journamalism.
That way, you're finished by lunchtime, and can go and powerlunch with other members of the Cool Kids' Table.