They made/are making the same argument about Bush's UN appointee John Bolton (which is why Bush is appointing him during the August Congress recess).
I'm with John Marshall when he says:
Out of the corner of my eye I've been watching this growing dispute over whether and which 'documents' about Judge Roberts the White House will turn over to the senate as part of his confirmation hearings. And quite apart from the particular documents in question, I'm wondering what the argument is, precisely, for the White House having access to any more information in the process of nominating Roberts than the Senate should have in confirming him.
It seems like a basic point of logic. Why should the senate's call be, by definition, less well-informed than the president's?
I'll go one step further. If he is a good canidate and you want him at this important job, what reason do you have for withholding information?