So now six of the former US Attorneys have come to Capitol Hill to provide testimony. Two of the six have alleged clear instances in which members of Congress or their aides tried to pressure them into either pursuing or hastening corruption investigations against Democrats. A shadow hangs over the circumstances of the firings of the remaining four -- particularly that of former San Diego US Attorney Carol Lam who was in the course of pursuing one of the biggest corruption investigations in US history when the ax fell.

If this were a preliminary hearing or a grand jury and we were trying to ascertain whether probable cause existed to move on to a full investigation I don't think there's any question that the burden would have been met in today's hearings.

In this case, that means a full investigation. The prosecutors themselves can only speculate -- based on various pieces of evidence -- about why they were fired. The people who know are in the Justice Department and in the White House. Most awkwardly, for a congressional investigation, they're in Congress itself.

It's time to call up the people who really know, put them under oath and find out what happened.