NEW YORK — It would be hard to identify a work for the theater with its finger more cogently and rewardingly on the pulse of America right now than “What the Constitution Means to Me,” Heidi Schreck’s deeply affecting traverse of the intersection between a nation’s defining legal document and that nation’s continuing struggle to implement it.

The endearingly funny evening Schreck has devised and Oliver Butler has directed — a monologue wrapped in a three-character performance piece — puts you contentedly in mind of one of our inalienable rights: the pursuit of happiness. Writer-performer Schreck is herself the quintessence of the happy warrior, enumerating for us the marvels of the Constitution even as she reveals the ways in which it has been used against some of its own people.

The play’s title alone is an achievement, for rarely in modern times has a tangle with the intentions of the framers felt more vital to saving our imperfect union. The crosshairs of “What the Constitution Means to Me,” which had its official Broadway opening Sunday at the Helen Hayes Theater, are not trained on the current administration in Washington per se; Schreck’s 100-minute narrative concentrates more forcefully on the gaps in our system that left women and minorities at the mercy of the white male establishment that designed it.

The psychic undergirding of the show, though, is an audience’s willingness to believe that the Constitution is under threat — and equally, that it remains the instrument of national salvation, even for those it has not always adequately protected. And these are the people for whom Schreck is speaking, as she intersperses accounts of the history of her own family in small-town Wenatchee, Wash., where beatings and other even more horrific forms of abuse were endured by generations of her female relatives.

Wenatchee is where “What the Constitution Means to Me” ostensibly takes place. Schreck tells us that she paid for her college education with prize money from the American Legion-sponsored contests she entered, in which high school students speechify about the personal significance of various amendments to the Constitution. The set, by Rachel Hauck, is of a modest legion outpost with a wall adorned by black-and-white photos of 163 legionnaires. In the guise of her 15-year-old self, Schreck re-creates one of these competitions, under the supervision of an American legionnaire played with humorous humorlessness by Mike Iveson.

The contest personas will eventually come off, allowing Schreck and Iveson opportunities to underline incisive personal connections with the amendments Schreck analyzes, among them, the equal protection and due process clauses of the 14th Amendment. Along with an illumination of how prejudicial interpretations of these clauses failed them both — and particularly, of women facing physical attack by men — there are moments of poetic insight into how the Constitution works. One of the winningly lyrical passages of the play concerns Schreck’s exuberant remarks on the short-and-sweet Ninth Amendment, which declares that rights laid out elsewhere in the Constitution “shall not be construed to deny or disparage others retained by the people.” (Worry not, clock watchers: The evening goes into detail on only two amendments.)

Schreck is key to the play’s advanced level of enchantment. It’s her self-effacing buoyancy that sustains the piece, even at the few moments when it teeters on the brink of excessive digression. She has mastered the illusion of spontaneous confession; you imagine that she is revealing just for you the news of her teenage crush on the late Patrick Swayze and her complex feelings for her Grandma Betty — even though she has performed versions of the piece since originating it off-off-Broadway at Clubbed Thumb a decade ago. (Schreck and the show were supposed to be the springtime offering at Washington’s Woolly Mammoth Theatre, but the engagement was canceled after “Constitution” proved a hit last year at the New York Theatre Workshop, and a Broadway run then intervened.)

That the play still exists in the present tense for her was abundantly clear at the critic’s preview performance I attended, when a particular memory caused her some visible upset and she had to pause to gather herself.

And she did, splendidly. Although much of “What the Constitution Means to Me” is cautionary, the evening concludes on a high note: Schreck invites a female New York City public school student to join her for a final constitutional debate. In separate viewings, I have seen both participating students, Thursday Williams and Rosdely Ciprian, and can attest to their wit and poise. Both are such impressive representatives of their generation that you will leave the Helen Hayes a little more optimistic, knowing that the Constitution means so much to them.

What the Constitution Means to Me, by Heidi Schreck. Directed by Oliver Butler. Costumes, Michael Krass; lighting, Jen Schriever; sound, Sinan Refik Zafar. About 100 minutes. $49-$199. Through July 21 at Helen Hayes Theater, 240 W. 44th St., New York. 212-239-6200.