Nancy Reagan as poetry slammer? Well, why not? In this "amorality play"--evolved from his old Saturday Night Live routines, and sharpened considerably in response to both Mrs. Reagan's memoir My Turn and Kitty Kelley's unauthorized biography--Terry Sweeney offers a deliciously funny portrait of the former first lady that's simultaneously impeccable and improbable. Fancy Nancy delivering her original doggerel on such topics as Americanism, feminism, Hollywood homosexuality, dressing well, and stepdaughter Maureen ("Ode to an Overeater"). Then, trouper that she is, the girl who put the zing in the right wing launches into her musical comedy material: "If I Ruled the World," a pseudo-Oriental number with fan-waving moves left over from when she did Lute Song on Broadway with Mary Martin, and the inevitable "Rose's Turn" from Gypsy (with her own lyrics, of course). Backed by a gigantic American flag that puts one in mind of George C. Scott's Patton, Sweeney's Nancy also lets us in on her thoughts on Barbara Bush ("Lord knows she's doing her best--isn't it sad?"), Imelda Marcos and Leona Helmsley ("Who's next?!"), Jesse Helms, "Raisinface" Raisa, and her completely innocent encounters with Frank Sinatra and Mikhail Gorbachev (Ronnie's in there too, somewhere) before parrying prescreened audience questions in a "people's press conference." Sweeney's a gifted and precise comic actor, and his physical impersonation is hilariously on target-the wide-eyed, mock-innocent gaze, the trimly arranged hemline of the red skirt around the tightly clenched knees, the paranoiacally prim walk, and the coyly condescending set of the mouth as Nancy strives to convince us of her concern about the state of the union. Halsted Theatre Centre, through June 9. Wednesdays-Fridays, 8 PM; Saturdays, 6 and 9 PM; Sundays, 7 PM. $15-$20.