It's the question of the moment inside the Beltway and most people I've talked with tend to think he's trying to rewrite history, get his spin out there, ensure that his argument gets heard. That theory makes sense. But something also seems lacking. There's no immediate payoff, and politicians are rarely compelled to campaign for the history books; at least, not until several years have passed since the end of their administration. That's what Bush is doing. So this strikes me as a better guess:
By relentlessly taking to the airwaves, Cheney is re-politicizing issues that should be strictly legal ones. And as long as the issue of law-breaking remains political, and not legal, in nature, Cheney and his cohorts Donald Rumsfeld and former Attorney General Alberto Gonzalez can rest easy. By becoming the voice and face of the Bush administration’s wrongdoings, Cheney is gambling, so far correctly, that Obama won’t have the political guts to pursue him.
Cheney knows he has no legal defense. His best play is to continue to ratchet up the rhetoric and make opening up the investigation politically unpalatable. The Obama folks, in response, are slowly releasing previously classified documents and trying to let public perception overtake political leanings. It's a game of high-stakes politics that Cheney will ultimately lose. The only question remains whether he'll be declared a war criminal while he's still around to see it.