It seems to me that Miers wasn't done in from a lack of conservative cred as the wingers want to believe. Bush was convinced she was like him and would've fought for her all the way through. She was done in from simple incompetence. Her responses to committee questions betrayed a complete lack of understanding of constitutional law. Her meager writings were incoherent. She was unable to articulate competence in meetings with senators.
Give Miers the same set of facts but with Judge Roberts' obvious competence on legal issues, and she gets confirmed. She wasn't done in because the crazies flipped. She was done in because she simply wasn't competent to sit on the High Court and it was so painfully obvious.
I point this out not to gloat or throw my lot in with Kos (clearly, I'm already there), but to mark this post for the future, since I suspect three weeks from now we'll be hearing left-wing charges about how the new nominee is just red-meat tribute being paid to the Right-Wing Extremists. Which just isn't true.
This was always about competence.