Why does Scott McClellan feel so compelled to discredit today's report that George W. Bush knew in the fall of 2003 that Karl Rove had a hand in leaking Valerie Plame's identity?

Over at AMERICAblog, John Aravosis has sleuthed out two good reasons: If the report is true, Bush may have lied. And if the report is true, Bush may have lied.

The New York Daily News says that Bush and Rove had discussions about Rove's involvement in the Plame case "beginning shortly after the Justice Department informed the White House in September 2003 that a criminal investigation had been launched into the leak." If that's true, then Bush may have been telling something less than the full truth during a Cabinet meeting on Oct. 7, 2003, when he told reporters that he didn't know who leaked Valerie Plame's identity. "I mean this town is a -- is a town full of people who like to leak information," Bush said then. "And I don't know if we're going to find out the senior administration official [who leaked Plame's identity to Robert Novak]. Now, this is a large administration, and there's a lot of senior officials. I don't have any idea. I'd like to. I want to know the truth. That's why I've instructed this staff of mine to cooperate fully with the investigators -- full disclosure, everything we know the investigators will find out. I have no idea whether we'll find out who the leaker is."

Of course, the Bush-Rove conversations that the Daily News alleges occurred may not have happened by Oct. 7, 2003. But if they happened, they happened long before Bush sat down for an interview with special prosecutor Patrick Fitzgerald in June 2004 -- an interview in which Murray Waas' sources say Bush insisted that Rove had assured him that he wasn't involved in outing Plame.

If the Daily News is right, Bush lied to Fitzgerald. If the Daily News is wrong, Rove lied to Bush. Unless we're missing something, Mr. President, those are the only possibilities. Which is it?