Wes Pruden, in the middle of mocking Bill Clinton's brassiness for talking about the Libby deal given his own 11th-hour shenanigans, characterized Bush's Libby thing as "reluctant."
This seems to be part of the "Official Line," but like most such pronouncements from the Bushists, it doesn't stand up to the minimal standards of logic or sense.
If he was so "reluctant," it seems odd he'd act so quickly (just a few hours) after Libby lost his appeal. I would expect real reluctance to manifest itself in a decision put off until the last possible moment, not the first available one.
The simplest and most obvious explanation is that Libby was offered a corrupt deal, either explicitly or implicitly, that he's be taken care of as long as he kept his mouth shut. This theory matches the known facts much more closely than the alternatives offered by Bush's defenders.