If the White House has nothing to hide, why is it hiding?

Sen. Patrick Leahy:

This is a further shift by the Bush Administration into Nixonian stonewalling and more evidence of their disdain for our system of checks and balances. This White House cannot have it both ways. They cannot stonewall congressional investigations by refusing to provide documents and witnesses, while claiming nothing improper occurred. [...]

I will look at the President's broad claim of executive privilege. Since we have heard so much testimony that the President did not personally make these decisions on the firings and was not personally involved, it is difficult to imagine that there is much basis to these claims. They cannot have it both ways.