IMHO, Ed Whelan makes a point about sending Ginsburg up using the same logic as shown in my post. But,
1. that goes beyond credibility. It will SMELL like a political stunt;
2. As Behind Liberal Lines points out, the Chief Justice does get first crack at writing opinions whenever he is in the majority. For Kennedy, this means reiging in the left even when he sides with them; For ginsburg, it'll mean she becomes the wackiest left-winger becomes the voice of the majority whenever the majority tilts ever so slightly left.
3. I expect there to be another conservative added on, and so will Kennedy. Kennedy seems to like to be on a winnig team, and forsaking the right, only to be overpowered by a new majority, will impugn Kennedy's repuation. My bet is that he'd want to be seen as a poineer of the new majority, rather than vanquished by it.
We no longer like NR or NRO. Tell them to shape up.
Karl Keating on the Decline of the National Review and Other Matters