"What possible benefit does this have for the Dems" you ask?
Rove is responsible for methodically eliminating the democratic party in Texas from the top down. The man has an astute understanding of democratic vulnerabilities. Rove is a political genius in my mind. His understanding of politics goes far beyond what most of us are capable of understanding.
Well..to expand on that... I think Rove has mastered all the triggers to get his opponent to self-destuct.
It's like when you were kids and you knew you could always get a sibling riled up and just when they blew their stack you knew it would be about the time your parents showed up..thus getting bro/sis in trouble for responding to you setting the bait.
Maybe not a great analogy but I think it is close.