POWER PLAYS: HELEN, JOAN AND HALF-CRAZY CLAIR by Terryl Paiste; directed by Robert Schulte; set consultant, Russell Metheny; costumes by Bonnie Ann Stauch; lighting by Robert Marietta; with Stephanie Daneberg, Lucretia Norelli and Tanis Roach. MR. WILSON'S PEACE OF MIND, by Mark Stein; directed by John Healey Jr., with T.G. Finkbinder, Linda Mann, Bill Baker, Daniel Elsea, Martin Goldsmith, Jan Frederick Shiffman and Joe Montes. At the New Playwrights' Theatre through July 21.

At Pueblo, Colo., in September 1919, Woodrow Wilson delivered an appeal for his League of Nations that climaxed with a highly unpresidential, rather foolish and yet genuinely moving vision of enduring peace.

A few hours later, he suffered a massive stroke - perhaps brought on by the impossible load of high ideals, vanity and priggishness he was carrying about in his brain.

But the fragment of the Pueblo speech contained in Mark Stein's "Mr. Wilson's Peace of Mind," as delivered by T.G. Finkbinder, isn't moving in the least. Nor is his stroke. This is a Woodrow Wilson who wears his foolishness on his sleeve, and the surrounding play, although briskly written and imaginatively staged, never develops any serious dramatic tension.

It does, however, develop an engaging comic tension in the negotiating-table scenes at Versailles. As the bored Australian prime minister, Joe Montes looks as if he had just been knocked cold by Skylab, and Jan Frederick Shiffman, as Italy's Orlando, is marvelously mystified and flabbergasted by all of the Wilsonian posturings.

Stein's picture of Wilson quoting Robert's Rules of Order while the old World leaders grab for land is stylized but quite entertaining. Probably no one has ever summed up better than Wilson the insane mixtures of naivete and cocksureness in the American character.

But for half of a bill dubbed "Power Plays," Stein's work achieves a fairly meager voltage level.

The other half of the bill that opened last night at the New Playwrights' Theatre - the "curtain raiser" - is a whimsical fantasy in the life of a 12-year-old girl. In Terryl Paiste's "Helen, Joan and Half-Crazy Claire" an undersized, barely pre-adolescent girl becomes the battleground in an ideological war of wits between Joan of Arc and Helen of Troy.

This intriguing pair - Joan wearing a big fat ERA button, and Helen compulsively applying nail polish and peering into the mirror - attempt to win Claire to their divergent views of womanhood.

Paiste's short play take place in a locker room, where the tiny Claire squats atop a laundry hamper reading John Stuart Mill and weighing the advice of her two historical heroines.

"Is that all you think about, being pretty?" she asks Helen.

"Not at all," comes the reply. "I think about being beautiful." Helen's larger message is that "power is the only thing that matters - if you aren't born with it, you must achieve it through marriage." Joan, needless to say, sees things a bit differnetly.

This power play, too, might have trouble igniting more than about a 75-watt lightbuld, but it is a highspirited and carefully conceived piece of work.