“The West Wing,” debuting at 9 tonight on NBC, is a series that will challenge viewers.

The drama set inside the White House assumes that viewers have more than a basic knowledge of what goes on within The Beltway. Another built-in assumption is that they can keep up with a large ensemble cast, and that they can keep up with the show’s rapid-fire pacing and dialogue. If not, tough. “The West Wing” doesn’t pander or spoon-feed; there’s no asides to help viewers catch up.

As a result, not surprisingly, “The West Wing” is one of the most intelligent shows on TV, right from its debut tonight. No surprise that it’s created by Aaron Sorkin (“The American President”) and Thomas Schlamme (“Sportsnight”) and John Wells (“ER”), all of whom are quite adept with thinking-viewers’ series.

Martin Sheen (“Apocalypse Now”) plays President Josiah Bartlett, a politically adroit populist from New Hampshire (it could happen). His staff is played by a top-notch cast of TV and film veterans, including former Brat Packer Rob Lowe, John Spencer (“L.A. Law”), Moira Kelly (“To Have and To Hold”) and Allison Janney (“Primary Colors”).

The first episode shows the firestorms that flare up daily inside the White House. Lowe’s character discovers that he had slept with a prostitute the night before. The president has crashed his bike into a tree, a situation that no amount of spin control can set right. The deputy chief of staff has enflamed the Christian right with an ill-conceived comment on a national news show. Then there’s those pesky boat people coming from Cuba.

“The West Wing” serves up life in a pressure cooker, in a town where rumor and innuendo are the currency in trade. Sure, the series is going to require quite a bit of concentration from viewers (tape it so that all the dialogue can be caught). But “The West Wing” is among the top new shows this fall, and is worth the effort.

The other new show tonight, “Oh, Grow Up” at 9:30 on ABC, isn’t nearly the polished creation that “West Wing” is.

Instead, the series is part of a mini-trend this year, sitcoms which explore the Peter Pan complex. Horndog Hunter (Stephen Dunham) and his buddy Norris (David Alan Basche) have been friends since college. Another college pal, Ford (John Ducey), recently decided he was gay, and he leaves his wife to move in with them.

Ford’s stunned wife, Suzanne (Rena Sofer, “General Hospital”), remains sullenly in the picture. Further complicating matters, the 18-year-old daughter Hunter never knew he had tracks him down, as she’s coming to town to attend college. So Hunter has to think about (duh) growing up.

“Oh, Grow Up” is marginally amusing, if the viewer can buy into the convuluted concept. It’s not the worst new sitcom this fall (there’s so many cliched entries to choose from), but up against the more innovative “Get Real” on Fox, “The West Wing” on NBC and “Roswell” on WB, “Oh, Grow Up” doesn’t figure to reach maturity.