Why would Tim Russert lie? Tom Maguire has a theory:

Well – as to Russert’s motive, this post has more detail, but the summary is this – Russert started with a little white lie to the FBI in November 2003, with the objective of concealing the fact that he (or Andrea Mitchell) had a source for the Plame leak. Russert did not “lie” to the investigators; he misled them with carefully phrased testimony so as to avoid subpoenas, jail time, and the disclosure of NBC News sources. And it seemed like a little white lie at the time – Russert knew that Libby had not leaked to him, so he reasoned that his chat with Libby was not the sort of primary leak (government official *to* reporter) that investigators were seeking. Russert maintained this charade with his deposition to the grand jury in June 2004, then blanched when he finally saw the indictment in October 2005 – the investigation had morphed from a search for leakers into a search for perjury and Russert had become a star witness. The most trusted man in news did not think he could keep his job if he came forward and admitted that he had misled the Fitzgerald investigation for nearly two years, so he kept quiet and awaited developments. And one of the developments was that subsequent court filings made it clear that no emails or notes existed at either the White House or at NBC to contradict his story. So at the trial last week, when faced between (a) admitting that he had misled investigators for three years, probably losing his job and certainly foreclosing any future stories about Big Russ and the Catholic nuns who taught him in school, or (b) continuing the cover-up, Russert took the final plunge and lied.

It’s at least as plausible as the prosecution’s theory that Scooter Libby lied to cover up a nefarious conspiracy to “punish” Joe Wilson — a conspiracy that even administration outcast Richard Armitage was in on.