Ed also writes:

It portends a showdown in the Supreme Court over the nature of executive privilege, and Sensenbrenner is correct. Absent any evidence of criminal conduct, the Supreme Court is highly unlikely to grant the legislative branch free rein to pursue contempt charges or to undo executive privilege.

This is simply uknowable but the case law, IF FOLLOWED, would lead to a prediction of exactly the opposite conclusion. As I wrote yesterday about the CRS Report:

Of especial interest to today's controversies are the discussions of Congress' power to investigate abuse and fraud and the inherent contempt power. On investigations of abuse and fraud, such as the US attorney firings, the report states:

Congress’s power “to conduct investigations is inherent in the legislative process. That power is broad. It encompasses inquiries concerning the administration of existing laws as well as proposed or possibly needed statutes.” The Court did not limit the power of congressional inquiry to cases of “wrongdoing.” It emphasized, however, that Congress’s investigative power is at its peak when the subject is alleged waste, fraud, abuse, or maladministration within a government department. The investigative power, the Court stated, “comprehends probes into departments of the Federal Government to expose corruption, inefficiency, or waste.” “[T]he first Congresses,” held “inquiries dealing with suspected corruption or mismanagement by government officials” and subsequently, in a series of decisions, “[t]he Court recognized the danger to effective and honest conduct of the Government if the legislative power to probe corruption in the Executive Branch were unduly hampered.” Accordingly, the Court now clearly recognizes “the power of the Congress to inquire into and publicize corruption, maladministration, or inefficiencies in the agencies of Government.”

(Emphasis supplied.) In the US attorneys firings scandal, the Congress' investigative power is at its zenith while the President's claim of executive privilege is at its ebb as it does not involve a question of national security. It does not even inolve communications with the President. Isn't it obvious why White House counsel Fred Fielding wants no part of a court adjudication of this dispute? Because he is sure to lose.

Really, Ed's "concern" is unfounded when he writes:

Nancy Pelosi will in all likelihood force a ruling that will firmly establish executive privilege and leave Congress with less power than it has had, after having finally called its own bluff.

Ed seems to not have a firm grasp on the material. Indeed, he does not even consider the possibility of an inherent contempt proceeding. I am not sure what he is relying on for analysis but he is far off the mark here. It is the President who is playing with fire regarding executive privilege, not the other way around.