I believe that the WH had been preparing hard for probable SC vacancies...expecting ther'd have two soon..the vetting had been done, and W, because he has a decisive management style, had decided on his two nominees..
Let's say that at the last minute, the weekend before the nomination was announced..that person backed out. Here are three possible reasons why..
1. They did not want to go through the whole ungly confirmation and background process..
2. Something in their record came up at the last minute
3. They felt that Roberts would be a very hard act to follow, so they chose not to do so...
So, the WH felt that they had to stay on pace..they could NOT wait another few weeks to search out another name..so Miers stepped up to the plate..to fill the void..
Unfortunately, he totally misjudged the reaction of his base who have seen so many other opportunities go awry in the past. This was our one chance to correct many of the social ills that afflict America -- often protected if not promoted by judges who are aggressively pressing their vision of America from the last federal bastion of Liberalism.
Schumer is behaving like a cornered animal because he knows he's in a fight for the survival of his ideas and his party. He won't be satisfied unless Bush nominates another ACLU General Counsel like Ginsburg, but he's content to let Republicans do his dirty work -- for now.