He just mention Baker's report
I'm going to be sick
This is done exactly as it needed to be. The investigations would have subpoenaed Rumsfeld and Bush would have had to invoke Exec. Priv. to prevent his testimony. This way, no such ongoing lightning rod will exist. Rumsfeld can testify all day long and the matter will be put to bed in a week or two.
And after that, nothing will change policy-wise, and come 2008 Hillary will still have to deal with the left wing, who generally hates her right now, because nothing will have changed.
This was a good maneuver. And the right time. No point in resigning yesterday because control of Congress might not have been lost and the subpoena power might not have existed.