The Delaware conundrum, Part Three

I’ve written before about the Delaware Senate race and, in particular, the Republican primary contest between Rep. Mike Castle and Christine O’Donnell. The winner will face popular county executive Chris Coons in November.
Today, the Tea Party Express announced that it is supporting O’Donnell. It’s reasoning comes down to the view that Castle is “one of the most vile RINO’s you will meet.”
The press release doesn’t explain why Castle is “vile” and I’m pretty sure the description doesn’t fit him. Castle is, however, a RINO, or perhaps more precisely a RIHHVO (“Republican in half his votes only”).
A recent Rasmussen poll showed O’Donnell (an ardent conservative) trailing Coons by 10 percentage. By contrast, Castle led Coons by a margin of 49-37. Thus, the Tea Party Express’s endorsement of O’Donnell differs in a crucial respect from its endorsement of Joe Miller in Alaska. Alaska is conservative enough that Miller will probably be elected, but Delaware is probably too liberal to elect O’Donnell.
Nominating O’Donnell would therefore strongly enhance the likelihood that this seat will remain in Democratic hands. This, in turn, would enhance the chances that the Democrats will retain control over the Senate and cost Senate Republicans a favorable vote about half of the time (Castle’s life-time ACU rating is 52.49).
But because Delaware is not much like Alaska politically, I don’t expect the Tea Party Express’s endorsement of O’Donnell to boost her to the extent it boosted Miller. In Alaska, moreover, the Tea Party’s endorsement was greatly enhanced by Sarah Palin’s support for Miller. Even if Palin gets behind O’Donnell, she will not have the same sway she had in her home state.
Nonetheless, the endorsement by the Tea Party Expresss represents a favorable development for O’Donnell and should put the Castle campaign on notice that it may have a fight on its hands.