Let’s pretend, for a second that all the other reasons why the cries of "runaway prosecutor" from the Libby Lobby don’t exist. Set aside the fact that the FBI and then Fitzgerald were investigating all leaks of Valerie Wilson’s identity, not just those to Robert Novak. Set aside the fact that the 1X2X6 story (as well as the clear evidence of at least three leaks by October 12, 2003) didn’t have the FBI looking for more than one leaker.
The claim that Fitzgerald should not have investigated beyond the the day when, on October 1, 2003, Armitage identified himself as the first source to Novak would still be wrong.
That’s because there were clear discrepancies between Armitage’s and Novak’s stories. And Fitzgerald was actively investigating Armitage and Novak at least until September of 2004. The FBI couldn’t close up shop on October 1, 2003, and Fitzgerald didn’t close up shop on December 30, 2003, because it was still trying to determine whether Armitage had leaked Valerie Wilson’s identity to Novak intentionally for at least nine more months.
The newly unsealed portions of the affidavits Fitzgerald wrote in pursuit of Judy Miller’s and Matt Cooper’s testimony make this clear (I’m getting these scanned–I should have links to them in the next day or so). In the Miller affidavit, Fitzgerald lays out some of the discrepancies: