"Nasty Habits," a movie adaptation of Muriel Spark's satiric novella "The Abbess of Crewe," which transposed the Watergate scandal to an English convent, might be more satisfying if the filmmakers had been able to resist outrageousness at all costs.

Now at the K-B Cinema, the film has its amusing conceits and interludes - especially when Sandy Dennis is permitted to steal scenes blind with her bespectacled stares, beaver smiles and hilariously twittery readings in the John Dean role, a fall guy named Sister Winifred.

Unfortunately, the level of funning is not as elevated as it might be. One would think that enough humor could be derived from Spark's original switches of sexes and institutional settings. But producers-screenwriter Robert Enders must have felt shaky on high comedy ground, because he ends up depending on the shock effect of cursing, carousing nuns for an excessive number of laughs.

By the time the movie winds down to a fadeout, the only source of humor appears to be Glenda Jackson as Alexandra, the scheming, hypocritical abbess, reiterating the most famous damaging remarks of richard Nixon, Jackson's readings are exquisitely plummy, and her performance tends to confirm what one suspected while watching the misbegotten "Hedda" - this actress may be evolving into a delightful interpreter of high comedy snobs and aristocrats. Nevertheless, the movie grows more dislocated with every fading reel, and there's something about her accent applied to Nixonian utterances that contributes to the dislocation. Failing to sustain an allegorical comic setting of their own, the filmmakers are reduced to mimicking Nixon in a British accent.

When the old abbess Hildegarde (the late Edith Evans) dies before being able to sanction Alexandra as her successor, Alexandra conspires with her Haldeman-Ehrlichman combination - Geraldine Page as the prioress Walburga and Anne Jackson as the mistress of novices Mildred - to guarantee her chances of election. The challenger, Felicity (Susan Penhaligon), is a liberated joke: a vain, sexually ravenous young nun who has organized a seditious sewing circle among the younger nuns in the convent. When a burglary attempt, aimed at abstracting incriminating love letters from Felicity's sewing box, backfires and results in the arrest of the burglars (a couple of mercenary seminary students), Alexandra and her cronies are forced into a cover-up and naturally fix on their flunky Winifred as a made-to-order patsy.

Enders has introduced facetious stands-ins for Kissinger anf Ford: Melina Mercouri as a globe-trotting diplomat called Sister Gertrude and Anne Meara as a likeable bumbler called Sister Geraldine. The movie could use more of the latter and total elimination of the former.

The just-messing-around aspects of the show are enhanced by the appearance in jokey priestly drag of Rip Torn, Eli Wallach and Jerry Stiller, the spouses of Geraldine Page, Anne Jackson and Anne Meara, respectively. I'm not certain exactly when "Nasty Habits" began to seem like an irreversible facetious drag, but it had worn out its welcome quite a few minutes before the house lights came up again.

Under the circumstances it might be advisable to slip out a trifle early. There are reasons for wanting to see the performances of Sandy Dennis and Glenda Jackson from start to finish, but not even witty actresses can help his movie finish strong.