Well, I've got mixed feelings about this. I don't think that Miers was really qualified to be on the Court. Even if she was, she was certainly not the most qualified. Purely in terms of the principle that Supreme Court nominations should be based on intellect, this is a positive development.
Previously, in my post Policy Versus Principle, I said that I supported Miers because she would not be an ideologue who would try and go on some culture war vendetta, that consideration for me outweighing her lack of qualification.
The question now is how much pressure Bush will feel from the social right wingers to nominate someone more clearly opposed to abortion and the constellation of issues surrounding it. Josh Marshall had this to say:
Despite the thunderings on the right, this nomination didn't go down because it had so many enemies or because those enemies were so strong. It went down because the nomination never found any reliable bank of defenders. She had no allies. And the White House was too enfeebled to create them.
The problem for the president — aside from the imminent forced rearrangement of personnel — is that each group that took a bite out of Miers will feel empowered. And those groups are so multifarious that the president's freedom of maneuver will be significantly curtailed.
Marshall says that the President is now going to be forced to choose someone that the right will see as a home-run, but I'm not sure that that's really the case. Bush has to pick someone that will satisfy everyone at once. He's hemmed in.
For the past several years, support of any Bush initiative has been the default, but that doesn't seem to be the case anymore. With 'trust' in Bush evaporating, politicians must reflect the change in public sentiment and also become more skeptical. The unity in the Republican party that formed behind Bush has fractured; the 'Group of 14' and Bill Frist's stem cell split being two examples of fissures with the executive branch.