If Jan Maxwell was a senator, Congressional gridlock might well be a thing of the past. That’s the only conclusion to be drawn from the five-time Tony nominee’s dynamic and affecting performance as an action-oriented, liberal Georgetown hostess in “The City of Conversation,” now receiving its world premiere at Lincoln Center’s Mitzi E. Newhouse Theater.

As savvy Hester Ferris, the doyenne of Washington, D.C., dinner parties, Maxwell operates in a time when politicians sweated out deals not by bellowing across aisles or shutting down government, but over brandy and cigars. “Dinner,” Hester’s son explains to his fiancé before one such occasion, “is always about something.”

The title of Anthony Giardina’s engrossing story, set across 30 years, comes from a designation once given the nation’s capital by Henry James.

As “City” begins, Hester is celebrating the end of the Carter administration and maneuvering to position her allies into the inner circle of what she’s certain will be a new Kennedy presidency. Colin (Michael Simpson, in dual roles), her only child, has just returned home from the London School of Economics, bringing along his fiancé, Anna (Kristen Bush), a budding Reaganite who clashes with mama the minute she’s in the door.

In these moments, we understand that Giardina’s work, though it will turn on events as dry as the 1987 Robert Bork Supreme Court nomination, is a drama about a woman trying to buoy her family while remaining loyal to the causes that have shaped her life. Inevitably, those forces clash, and the fallout spreads over six administrations.

Maxwell is a wholly magnetic presence, steely one minute, frail and vulnerable the next. She is as believable as a Beltway snob (“Who ever has come from Kentucky?” she snorts, in front of Colin, during a private moment) as a good Southern girl from Arkansas, who tells a visiting senator and his wife: “I've driven through Kentucky only twice, I'm sorry to say, and what I felt was how lush and beautiful it was.”

A decade after the first scene, Colin and Anna are raising a child, Ethan (a fine Luke Niehaus). Mother, father and grandmother are at odds over just who has the right to influence the young boy. As the milquetoast prodigal son and ever-more bold daughter-in-law, Simpson and Bush make for excellent foils to Maxwell—though it’s the scenes between Maxwell and Bush that are most charged, particularly once the topic has changed from political ideology to subjects more cutting.

Tautly helmed by Tony-winner Doug Hughes (“Doubt”), the play’s most significant plot twist relies on the audience’s acceptance that one’s political passions could possibly prove as weighty as they do in Giardini’s script. Perhaps that doesn’t characterize your family, but the characterizations here are so fleshed out and nuanced that it’s not tough to imagine.

There are super supporting turns from Beth Dixon as Hester’s widowed sister, something of a maid to the entire family, and John Aylward, familiar from his dozen years on NBC’s “ER,” as a jowly southern politician. Phillip James Brannon is excellent in the play’s final scene, set on the night of President Obama’s inauguration, when he arrives with a grown-up Ethan to confer with Hester.

“The City of Conversation” ends on an impossible note, one that asks whether achievements in society at large are worth carnage on a more intimate level. It’s a question that has particular resonance in the current political climate, and one that for Hester and the audience is, by play’s end, almost too painful to contemplate.

“The City of Conversation,” through July 6 at the Mitzi E. Newhouse Theater, 150 W. 65th St. Tickets: $77-$87. Call Telecharge, 212-239-6200.

Follow Robert Kahn on Twitter @RobertKahn