Reply #3: I think it's merely an extension of the same process.

[boxster]

The Republicans and the media knew that this was going to be a close race, regardless of who the eventual Democratic nominee would be.

So, to them, it made sense to begin the attacks as early as possible. In their minds, if they could effectively smear a couple of the more likely candidates, they could end up with a jumpstart in the general campaign should one of those candidates win the nomination.