Time magazine has a long, detailed piece on the dispute between the former president and his vice president over pardoning Scooter Libby and  why Cheney believes the failure to do so will diminish the Bush legacy:

For Cheney, however, the ongoing battles are an extension of the fight he waged for several years on behalf of Libby. Cheney, says an ally, believes that the true legacy of the Bush years is the uncompromising way he and the President waged the war on terrorism. But Cheney also believes that Bush cannot claim that as a legacy if he fails to protect the aides and officials who carried out the dirty work.

It is an increasingly lonely fight. But as Democrats edge closer to probing the Bush-era practices, perhaps including CIA interrogators, Justice Department lawyers and Cheney's closest aides, it appears his darkest fears may be coming true. Since Cheney was often the man responsible for the policies that are now under scrutiny, it is perhaps no surprise that he is leading the counterrevolt. "I think it is very, very important that we have a clear understanding that what happened here was an honorable approach to defending the nation," Cheney said on May 10. "There was nothing devious or deceitful or dishonest or illegal about what was done."

This is the case Dick Cheney made for years in the Bush White House, prevailing for a long time, until he was outnumbered and outgunned. And it is one he seems prepared to make, without Bush at his side, for a long time to come.