Arlene Spectre drives me crazy. And, by the way, where did this idea that a swing-vote (O'Conner) could only be replaced by a swing-vote? I don't recall seeing anything like that in any of our founding documents. Replacing swinging door O'Conner with a solid conservative would be the right thing to do.
You are absolutely right. The constitution doesn't give any formula for the composition of the SC. I think Bush is again going to nominate a solid conservative and let the fight begin. They can say all they want about bad mouthing Brown and Owen but this senate confirmed them. They cannot now go back and say they are too far to the right and then filibuster either one.