I think it's become clear why Attorney General Mukasey is waffling on he definition of "torture" -- and why others in the administration are doing the same. I don't think it's impeachment that concerns them -- not with a weak Congress and not in an election year. I think they're worried about something much more dire.
At a Congressional hearing this week, CIA Director Michael Hayden admitting that waterboarding had been used (and even named three people it'd been used on). That statement appears to have been intentional.
What appears to me, at least, to have been less intentional is that at the same hearing, Director of National Intelligence Mike McConnell stated that the CIA will only use the technique if it's approved in advance by the Attorney General and the President of the United States.
In 1998, the UN General Assembly voted in favor of a treaty that established a permanent international war crimes court -- it's the International Criminal Court at The Hague. The US opposed the treaty, but did eventually sign it. The ICC's charter includes genocide, war crimes, crimes against humanity (including torture), and so on. The ICC can, like other similar tribunals such as the ones established at Nuremberg and Tokyo post-WWII, try cases and impose sentences. Documents explaining the functioning of the court may be found here:
International Criminal Court - Establishment of the Court
In May 2002, the United States repudiated its signing of that treaty. It's unclear to me what that really means vis-a-vis the jurisdiction of the court, but then again I'm not an attorney and it would probably take someone highly knowledgeable about international law to sort that out.
But regardless of the legal technicalities: I think the steadfast refusal by the A.G. to declare waterboarding torture and the repudiation of the treaty have the same purpose. They're both designed to minimize the likelihood that the President could find himself in the dock at The Hague . I think they know they're cooked and are frantically trying to identify and exploit any legal loopholes available to forestall that possibility -- which is why we continue to see increasingly-awkward tapdancing around the problem.