"they've testified before"

The Outlook staff at the Washington Post note that the Congressional Research Service determined in 2003 that presidential staffers have testified at least 73 times since 1944. Read a few examples here, including quite a few Clinton staffers summoned by the Republican Congress...

So why won't the de facto Bush White House offer up their people to discuss this US attorney issue? 1) Their "unitary executive theory" says that the President and his staff are not subject to any scrutiny. 2) They are hiding the real scandal behind the firing of the 8 US attorneys.