Meanwhile, the U.S. Senate today approved 94-2 a bill which would strip Gonzales of his authority to fill U.S. attorney vacancies without Senate confirmation. It places the law back to what it was pre-Patriot Act.
UPDATE: Think Progress reports that there is no precedent barring White House aides from testifying before Congress.
UPDATE II (from Xanthippas): Here's Glenn Greenwald, who thinks that the Bush administration actually doesn't have a leg to stand on when it comes to refusing to comply with Congressional subpoenas.
...it is crystal clear (just as it was when Bill Clinton sought to invoke "executive privilege" to resist Grand Jury subpoenas to his aides -- Sidney Blumenthal, Bruce Lindsay and Hillary -- in the Lewinsky investigation) that the narrowly construed doctrine of executive privilege does not entitle the President to shield the communications here from compelled disclosure. When the U.S. Supreme Court in U.S. v. Nixon (1974) rejected Nixon's invocation of that privilege to resist a Grand Jury Subpoena for the Watergate tapes, this is how the Court defined its scope (emphasis added):Of course, as Greenwald notes later (citing a 1998 William Safire article) Clinton's stonewalling "bought him four months." How much time can the Bush administration buy with theirs?The President's need for complete candor and objectivity from advisers calls for great deference from the court. However, when the privilege depends solely on the broad, undifferentiated claim of public interest in the confidentiality of such conversations, a confrontation with other values arises. Absent a claim of need to protect military, diplomatic, or sensitive national security secrets, we find it difficult to accept the argument that even the very important interest in confidentiality of Presidential communications is significantly diminished by production of such material for in camera inspection with all the protection that a district court will be obliged to provide.Similar reasoning was invoked by District Court Judge Norma Holloway Johnson in her decision denying Clinton's attempt to rely on this privilege to resist Ken Starr's subpoenas.
UPDATE III: Whoops! Turns out six of the eight U.S. attorneys fired by the Justice Department ranked in the top third among their peers for the number of prosecutions filed last year. There goes that "performance" argument...
UPDATE IV: I didn't think after Bush's press conference the White House could look more like the Nixon administration during Watergate, but yes, they can:
"In DOJ documents that were publicly posted by the House Judiciary Committee, there is a gap from mid-November to early December in e-mails and other memos, which was a critical period as the White House and Justice Department reviewed, then approved, which U.S. attorneys would be fired while also developing a political and communications strategy for countering any fallout from the firings."
UPDATE V (from Xanthippas): Can we say "line in the sand"?
UPDATE VI: And the Senate too!