The Times editorial page tries to issue-spot potential crimes in Republicans' dealings with federal prosecutors, but apparently ran out of time before writing the other half of its exam paper: the defenses that would be thrown up against such prosecutions. (The moderate conclusion "It is far too soon to say that anyone committed a crime, and it may well be that no one has," implies that Examsoft didn't eat the end of their writings.) First of all, one statute on which the Times relies heavily is 18 U.S.C. § 1512 (c), part of Sarbanes-Oxley and thus in a parcel of legislation that has gotten so much criticism that even one of its named sponsors has admitted that it needs "refinements." Having it used to go after White House officials and a senator would be the final nail in SarbOx's political coffin.
As for the specific enumeration of potential charges: Gonzales plausibly can say that he does not view prioritizing election fraud prosecution as a "political" reason to change U.S. attorneys. A federal prosecutor who isn't on board with this Administration's preferences, as dimwitted as those may be (Gonzales is following up on Ashcroft's anti-porn crusade), is going to be seen as a bad prosecutor. It is stupid of the White House not to specify what it meant by "performance," because most people assume it to refer to basic competence rather than pursuit of a particular goal among many reasonably possible ones, but it's unlikely to be a prosecutable stupidity. Similarly, a Republican nagging a prosecutor to hurry up election-related indictments before another election occurs is sketchy but would make a bad case. (The unrecognized irony of the editorial is that it's urging prosecutions without a strong likelihood of success -- exactly what Senator Pete Domenici seemed to be doing to U.S. attorney David Iglesias.)
The one area where the firings may have been definitely, inappropriately, and perhaps illegally political was the removal of prosecutors who were investigating Republican congressmen and lobbyists. For the White House to say that prosecutors should turn their attention away from misdeeds by members of the president's party no longer sounds like a difference in policy priorities -- it sounds like an attempt to corruptly obstruct, influence, or impede an official proceeding. But even here, if the U.S. attorneys can be shown to have engaged in wasteful, harassing investigation of Republicans who ultimately were shown to be quite innocent, their firings can be justified on the ground that they themselves were overly political, carrying a vendetta against Republicans instead of serving the people.