Think Progress reported this afternoon that White House spokesperson Dana Perino told reporters Friday during a press conference that the White House could possibly stop McClellan from testifying before Congress:

QUESTION: Could the White House block him from testifying, if he wanted to testify? Or how does that work?

PERINO: Conceivably?

QUESTION: Yes.

PERINO: Hypothetically, which I'm not supposed to answer a hypothetical, yes, I think so. The law would allow for that. But by saying that, I'm...