Judges Kozinski and Thomas say no. Judge Kozinski, for whom I clerked, is a Reagan appointee, and Thomas is a Clinton appointee. Important reading for those who follow this debate.
Judge Kozinski sent me this, responding to Orin's post that in turn responded to Judge Kozinski's and Judge Thomas's anti-Ninth-Circuit-splitting op-ed:
Orin Kerr makes an excellent point about the desirability of merging circuits. Merging circuits would probably result in increased efficiency, and ensure the delivery of a variety of services that are now unavailable in smaller circuits — such as Bankruptcy Appellate Panels, appellate mediators and appellate commissioners. Any merger proposal would, however, face a series of political obstacles. The judges would be required to cover a larger territory than they're used to, and merger would inevitably cause some to lose seniority and possibly forego a chance at becoming chief judge. States, too, may feel reluctant to become part of a larger circuit, where they may hold hold less sway. We know that this is the likely reaction from the relatively modest proposal a few years ago to add Arizona to the Tenth Circuit. Doing so would have upset the Tenth Circuit's seniority structure and the judges there let it be known that they were opposed — and that killed the proposal.
Orin's point — whether genuine or ironical — does not address whether splitting the Ninth Circuit makes sense. Merger of other circuits might be a good idea or it might not be, but the fact that circuit merger is not under serious consideration reflects mainly political inertia.