Two massive hurdles stand in Fitzgerald's way. First, the indictment's 22 pages fundamentally boil down to allegations that Libby lied, both to FBI agents and to the grand jury, about what happened during conversations with two different reporters: one with NBC's Tim Russert on July 10 or 11, 2003, and one with Time's Matthew Cooper on July 12, 2003. In the absence of a tape recording of these private, off-the-record conversations, the prosecutor's hurdle will be to prove beyond a reasonable doubt that the reporters' recollections of these conversations represent what actually happened; in other words, that Libby's testimony was false. This could easily amount to little more than a "he said/she said" swearing contest, and juries justifiably often demand far more from prosecutors before deciding to send someone to prison.
Second, even if Fitzgerald is able to persuade the jurors to accept Russert's and Cooper's recollections of events, the fact that Libby testified falsely does not, by itself, make him guilty of anything. Under the law, Libby cannot be convicted of perjury, making false statements or obstruction of justice unless the prosecutor can persuade the jury beyond a reasonable doubt that Libby knew he was lying at the moment those words left his mouth and that he uttered those words with the intention of deceiving the FBI and the grand jury. It's not nearly enough to prove that Libby got it wrong. Fitzgerald's team must prove that he did it on purpose.
The long and short of it is that, no matter how at odds with circumstantial evidence it may seem, an individual's good-faith belief that his statements are true is an effective defense. It could work for Scooter Libby, too.
Continuing with the notions that have been on my mind since the indictment, I find myself wondering: if Fitzgerald felt, for reasons of pride or ego or simply because he didn't want, as a career Justice Department prosecutor, to be labeled as a Republican stooge if by chance the Democrats won the next election, that it wasn't feasible to "no bill" the whole thing, wouldn't the next best thing be to indict someone for something known to be hard to prove, in a very narrow indictment; talk a lot about how "serious" it was without indicting for the things he considered serious; and then lose? Then you can give one of those "we swung and we missed" speeches, or talk about how the powerful can get away with things that mere mortals can't --- and there's always the chance that, with a DC jury and the legacy press coverage, you might just get a conviction.
Oh, it'd cost Libby a couple million dollars for defense, and the Federal government millions to try, but isn't that better than risking your career?