Here's how I think it might work:
Increased international pressure on the issue of war crimes. Rumsfeld is already feeling the heat from Germany with Bush, Cheney, and the rest of the gang to follow.
Democratic oversight will slowly but surely begin to uncover the mess of corruption that has been the raison d'etre and modus operandi of the Bush/Cheney administration. These details will add up, inexorably, to impeachable offenses.
The Dems would be wise not to push impeachment but just let the momentum build as the graft and fraud and waste and abuse add up to a damning indictment of the Bush/Cheney years. Let the criminality become obvious.
Nancy Pelosi will become President Pelosi and George W. Bush and Dick Cheney will go to jail which is only what they deserve but what we, the American people, desperately need in order to regain our self-respect and democratic republic.
We let Nixon off the hook and it led to the present debacle with Cheney and Rumsfeld coming back from the Watergate gang. Now we have Gates with all his Iran/Contra experience, another set of impeachable offenses we as a people were too timid to drop the hammer on. We can not let this happen again. If we do, we deserve everything we get.