It’s hard to tell which is most misguided — director Terry Johnson’s early choice of establishing the role of Mrs. Robinson, that classic lascivious lush of “The Graduate,” as the play adaptation’s celebrity linchpin, or merely the casting of Morgan Fairchild for that slot in the current touring production of the Broadway show.

It’s a terribly difficult role to make interesting. At heart Mrs. Robinson is a means to an end, a drunken plot complication for young Benjamin Braddock to trifle with and ultimately rebel against in his search for identity and love.

Perhaps greater actresses, like Kathleen Turner, the Broadway original, have and could have found richer flesh in the role. We can only venture a guess. Fairchild, 54, has the drunkard down pat, from her slightly shrill slurring words to a composure that hints of long-ago elegance trumped by a sad kind of resignation. But hers is a one-note delivery, never rising to the call to make Robinson something more, something compelling on her own.

(On a side note: Yes, Fairchild takes off her clothes for an early, much-
ballyhooed scene. And yes, she's surprisingly well-kempt. And yes, we’re pretty sure they’re fake.)

It’s a shame — Fairchild’s one-note character delivery is, not whatever apparent surgical augmentation — because without an interesting Mrs. Robinson, the weight of the show is on the shoulders of its young stars, Nathan Corddry as Benjamin and Winslow Corbett as Elaine, the Robinsons’ collegiate daughter, for whom Benjamin ends his adulterous tryst with mama and instead promises eager fidelity and a new life together.

The two young actors hold the show up well enough, and theirs are the most captivating scenes in the play. But Corddry has none of the sly charm of Dustin Hoffman in the 1967 film version — Corddry is more timid, a kind of Steve from “Blue’s Clues” mixed with Holden Caulfield, which, mind you, makes Benjamin’s bouts of nookie with Mrs. Robinson funny on a different level, and makes his bouts of self-loathing a bit more acute. Meanwhile, Corbett — a stubby-legged beauty with no discernible expression beyond the 10th row, takes her pittance of a role and, by the meatier second act, makes something adorable and tender of it.

On a brighter note, the play attempts to compensate for the movie’s artful cinematography with its own gorgeous uses of lighting and darkness and sets — creamy walls of louvered doors — that morph like secret puzzles to play for different scenes, from hotel lobbies to small bedrooms. It’s a successful substitute, one that helps make this “Graduate” still a reasonably enjoyable evening of light theater.