By Jove! Good-bye Rove!
Clearly, Hillary has been showing growing signs of strength as a candidate. She's buttoned up, on message, smart, and (gasp!) even funny. The more the public sees of her, the less threatening she seems and the better her poll numbers look. If I were the R's, I'd be scared too. Rove is trying to slam her hard and early, trying to knock her off her stride.
I think he's also trying to stir up the Republican base. Now that Bush has alienated just about everyone save the hardcore Republican nutters, it's in the party's best interest to keep throwing red meat to the only folks left in their camp. And, oh boy, the far-right nutters do hate Hillary. She's exactly the kind of woman who scares the pants off 'em: smart, powerful, and strong.
So, it's not so surprising that Rove has gone on the attack against Hillary. Once a bully, always a bully.