I had wondered about this, which effectively preserves the status quo (with O’Connor on the Court until yet another successor for her is found).

Roberts will of course be confirmed, a foregone conclusion even before this additional pressure was placed upon the Senate. We’ve seen the playbook of the "living constitution Left," and we’ve seen how little effect they can have, either on public opinion or on the Senate. As a result, the President can confidently nominate another judicial conservative. And he should, as soon as decency permits. (You know my preference.)

Update: More here and here. It’s clear that Sandra Day O’Connor could complicate matters, if she wanted to. But it’s not clear that someone who holds the substantive opinions attributed to Roberts will suffer any more from the assaults of the opposition than he has, so long as the new nominee and the Bush Administration have the stomachs for it.