If Rhenquist would have been the first, the 'Rats would probably have let a strict constitutionalist through since it would have not forced the change of the filibuster rule nor would it have changed the balance of the courts. But O'Connor is as often on the left as on the right and is often the swing vote. They will fight hard to make sure that she is replaced with another "moderate" or even a hard leftie.
I hope O'Connor is the first resignation for that reason.
If they let a conservative replace rehnquist without a filibuster, something I'm not sure they'd do anyway, they'd use that as leverage in a Judicial fight as signs they are 'reasonable". I want the Fourteen, and our seven Dwarfs specifically, put on the spot with the first resignation. O'Connor retiring would do just that.
She was the deciding vote on the Bush/Gore decision on 12/00.
Trust me, the far-left has no love for her. If anything, I hope she has 24/7 security for her and her family.