A TV series change-up (an episode that deviates far from the norm) is a risk. Often it is met with audience frustration, indifference, or annoyance and often this reaction is unfair (Take the brilliant episode "Point of View" from M*A*S*H or "Jose Chung's 'From Outer Space'" from The X-Files). Often, however, the change-up is nothing more than a ploy, a way to shake things up -- and usually to add life-blood to a dying series. Although The West Wing was far from dying at this point (There were many great episodes from Season 4 to come), The Long Goodbye is an example of what the series would be like without Aaron Sorkin and without proper "interference" in making this series how it should be made.
The Long Goodbye has many good things going for it. Mucho screen time for Allison Janney (always a plus) plus a downright stunning performance from Donald Moffat as the ailing father of C.J. This episode is unnervingly engrossing in its story, giving an intelligent "due" to the disease that is plaguing elderly America. Perhaps the best example of this is the fishing scene where Mr. Cregg goes off on a tangent and suddenly loses everything about himself. He doesn't recognize his daughter and is totally unaware of his surroundings. The scene is absolute power.
But what is it doing on this show? The West Wing is and always has been about, well, the West Wing. The story is usually about the political stories (usually at the expense of personal backdrop -- personal characterization just emphasizes rather than explains the storylines). Personal issues certainly exist on the show, but they do not dominate as in this episode -- and if they do, they eke themselves out through the "job" context. Think of Noel, the holiday episode from Season 2, where Josh has post-traumatic stress syndrome -- but this is expressed via his behavior at his job.
When you take the West Wing out of The West Wing, you lose the whole context, the whole comforting feel, out of the show (Here's one reason I dislike Seasons 6 and 7 so much). The Long Goodbye, unfortunately then, feels like a ploy -- a way to liven things up, in a downright depressing and somewhat manipulative way. It seemed a way to get Allison Janney her due (and it did, but she deserved it for all of her episodes -- not just this one) when she really didn't need it.
Furthermore, there were elements of the episode that seemed unforgivably forced and manipulative. I despised the Marco Arlens character (played by Matthew Modine) and felt there was no need for him. I thought several of the supporting characters were in there as plot devices rather than important elements of the story. Finally, the pace of the episode, though generally slow and atmospheric, seemed occasionally inconsistent. This would become typical for Alex Graves directed episodes down the line, but here at least we find that he has not fallen down the pretentious path he has yet.
So, even though Janney and Moffat were superb and the story itself was well-thought-out, this episode flops like a fish out of water. It was an unwelcome, if somewhat moving, aside in a show full of top-notch efforts.