Start with Ace who has a detailed post on why he can't support Christine O'Donnell for Senate and is opting instead for RINO Mike Castle:
That is to say: We cannot win full control of the Senate without a Republican in this seat. This seat has long been one of the seats we were just assuming we would win. Because Castle has been comfortably out front for a long, long time. This is not some longshot pick-up where it really makes little difference because we have no realistic chance anyway, so might as well swing for the fences. We have been counting this as an easy pick-up. When you read "Republicans will pick up at least 7 seats" this is number two or three on that list, after the gimme Arkansas pick-up. And we're going to toss this away? For what? She can't win. Period.
You need to read his whole argument. The upshot is that he'd rather have RINO Castle in that seat than a Democrat and to vote for O'Donnell in the primary is to hand the seat over to the Dems in November.
Stacy and Smitty aren't moved by Ace's argument and are still putting their money on O'Donnell as is Michelle Malkin who makes the case that Castle is a RINO who supports cap and tax; I don't think anyone disagrees with that assessment. But, we're talking about Delaware.
At Hot Air, Allahpundit is in Ace's court, asking "What exactly would be accomplished by nominating her," seeing an easy defeat in November if she wins the primary.
I guess it depends on if you want to send a message to RINOs like Castle that true conservatives can't support your blue votes, or if your concern is all about taking back control of the Senate, even if you have to vote for a RINO who won't vote your way all the time. I don't think anybody ever expected Scott Brown to vote like a true conservative 100% of the time, and he hasn't.
Dan Riehl can't support Ace on this one either:
As I've said in an email to a few, if someone has issues with O'Donnell, I don't think they should support her. But, helping Castle run her down is stupid, when one could just as easily have posted to help Angle, or Miller, or Rubio.
Even Mark Levin stands up for O'Donnell in an email to John McCormack of The Weekly Standard. In an interview with McCormack, O'Donnell admits to using campaign contributions to pay her rent on her townhouse. Levin asks:
Um, John, is this really a thoughtful interview? Where is she on the issues that I and millions of my listeners care about? Did you not want to delve into them for some reason? Also, who pays Castle's rent? Well, let's see, he's been on the government payroll for how long? I guess we, the taxpayers, pay his rent. You can do better.
McCormack's interview is here.
You can watch more of the online debate via Memeorandum.
In the end, I suppose Delaware voters will go for Castle; he's got a comfortable lead, and again, it IS Delaware. That's not to say that O'Donnell's message is in anyway off base; she's got all the right conservative positions. It comes down to the question of whether you vote for your principles or you vote for who you think can win, and that's a question the voters in Delaware will have to consider on September 14.