"The politics are what sells it, partly. It's a pretty simple ideology, accessible and easy to follow. So it picks up a whole bunch of followers, who aren't getting this from their TV in other ways.
"The ideology is also tied to Clinton. President Bubba's famous shift to the center spawned a lot of guilt in leftist supporters, who get to watch Sheen do what they wanted, but mortgaged/gave up/argued themselves out of. With W. as pres, the show could look openly oppositional, if it had cojones, which it doesn't.
"The show is also monologic, in lit crit terms. There's no real dialogue between forces, no real argument. The preaching is steady, never seriously argued....West Wing doesn't really allow any other views to appear as legit. This makes it easy on the brain.
"Another thing: the regional bias is ferocious. The entire staff is drawn from the Northeast and the West Coast, probably without modern precedent. Check out other, good White House films: Seven Days in May, Fail-Safe, the underrated Twilight's Last Gleaming. They all have characters drawn from the Midwest and South, reflecting the political realities of the country (duh). But Sorkin hates the South, and doesn't seem to realize the plains exist. Hence the Evil Racist Assassins being Southerners -- and arrested at a restaurant called "Dixie Pig" or something. This feeds into a lot of easy regionalism.
"Last point: the show's openly melodramatic, and that simply sells. Lots of the audience, I bet, doesn't think much about the politics. It could take place in imperial Rome, any Shogunate, or Dallas. Maybe not Dallas."
I think Bryan's probably nailed it. I have to disagree, though, about Seven Days in May being a good White House film -- I really expected to like that movie, but found it surprisingly clumsy. When John Frankenheimer died, I was disappointed that so many critics devoted so many column-inches to that picture, while generally ignoring my favorite Frankenheimer film, the surreal and PhildickianSeconds.