I don't think the Congress should join the issue over Executive Privilege by going after obscure White House staffers. We want this case argued on the best possible facts, both before the courts and in the court of public opinion.
I've previously suggested a subpoena to Scooter Libby, demanding that he tell what he knows about how the decision was made to wreck Valerie Plame Wilson's career. But the latest polling suggests an even better target: Dick Cheney himself.
First, he's the least popular member of the Bush Gang, which is saying quite a lot. I'm not sure whether he's more popular than the Unabomber, but it must be a close call.
Second, he has no Constitutional function except presiding over the Senate and (in Tom Lehrer's immortal phrase) waiting for the phone to ring. There is absolutely no basis in history, law, or logic for the claim that the Vice President can't be subpoenaed before the Congress.
Third, though we all laughed at his claim not to be part of the Executive Branch, in one respect that claim was true. If you define the Executive Branch as the set of people who have legal duties to obey the President's orders or orders given by people the President appoints, the Vice-President is not one of them. He is, in theory, an independently-elected officer. The President doesn't appoint him (except to fill a vacancy), the President can't fire him,
http://www.samefacts.com/archives/valerie_plame_/2007/07/subpoena_cheney.php(read the whole thing...its short...great rant