From an AP news article on the House approving subpeonas against presidential aides, "Bush said he worried that allowing testimony under oath would set a precedent on the separation of powers that would harm the presidency as an institution."
That just pisses me off. If anything has ruined the presidency as an "institution" it's been douchebags like Bush and Nixon. When you outright lie to the American people about every goddam move you make, sooner or later people begin to mistrust you and everything you stand for. Subpeona every fucking aide they can find and document every word of it, for a change.