The Wall Street Journal is reporting that President Bush will nominate Harriet Miers to succeed Sandra Day O'Connor on the Supreme Court. Miers is a trusted advisor and White House counsel. She had been rumored to be on the short list since last week.
The President was, evidently, looking for someone he believed he could trust who also hadn't left a paper trail a mile long for Senate Democrats to pick on. In addition, there's simply nothing for the Democrats to subpoena, since so much of her current work would be covered by executive privilege. Perhaps since Roberts worked in the Counsel's office, Bush went back to that well.
Here's a WaPo profile from June, before we knew there would be two openings.