I'm not ready to completely discount the possibility that there were changes in Cheney's personality over the 1993-2001 period. But a number of readers have suggested a more Occam's Razor friendly explanation that I find pretty convincing. In all of Cheney's earlier assignments, he held powerful positions under strong, at least fairly competent executives. Under Bush, especially during the first term, Cheney was, and certainly saw himself, pretty much in charge.

TPM Reader JB makes the point ...

I've always been pretty dubious about the whole Cheney personality change theory, and not just because Bart Gellman doesn't seem to give it much credence. I think it overlooks a much simpler explanation.

Dick Cheney acted as George W. Bush's Vice President in ways he did not as Gerald Ford's chief of staff or Defense Secretary under the elder George Bush because George W. Bush was not Ford and was not the elder Bush. I don't really think the matter is any more complicated than that.

During the younger Bush's first term especially, Cheney operated in ways that suggested he really didn't think his nominal boss was really up to the job. He treated associates not directly useful to him with contempt and disregard for their roles in the government -- something Ford would have discouraged and the elder Bush would have as well. George W. Bush barely noticed it, though he may understand it now.

Neither of the earlier Presidents Cheney served were giants. They were both career government men, sensitive about the prerogatives of their office and aware that their own success in public life was due to how well they worked within the rules, not how creatively they broke them. They also, in fairness to Cheney, did not experience anything like 9/11. Cheney earned his reputation for being smarter, shrewder and harder-working than most of the people he worked with in government. During the second Bush administration he had few checks on his authority, and after 9/11 especially felt an imperative to fill the vacuum left by his President's limited interest in the details of government.

Cheney could not have been Cheney if Bush had not been Bush.