I am sure that the votes were counted on each possible nominee before the appointment.
To put out a candidate who would placate the "base", but not get confirmed is unwise.
Forcing into the open the usual suspects, the Feminists, hard lefties is good political strategy.
To the contrary, one only need look to the confirmation battle over Robert Bork. His rejection went a long way toward energizing "the base" to get Republicans elected so they could support a Republican President in selecting conservative nominees.
What is unwise is appearing to capitulate when you were elected to defeat.
Furthermore, feminists don't care if they are forced into the open. They'll find some excuse to oppose Miers because of the President who nominated her.