bret, i would like to broaden out the conversation in anticipation of what we might hear over the next several hours of coverage and next several days of this story. our very own judge napolitano, charles krauthamer brought up this is constitutionally significant. we could see a real challenge to the constitution. even a constitutional crisis. what do we mean when we hear that? what should we know and are we really at this point with this story? >> reporter: clearly this is verging on the battle between the executive branch and legislate tiff branch here. once you exert executive privilege, it is a conditional privilege and it could be challenged in the supreme court to test whether it should be implicated in this use asserted in this case but once the president does that, invokes that, it indicates the executive branch is directly involved. the white house is somehow directly involved. it doesn't usually cover