Edward Gero as the late Supreme Court Justice Antonin Scalia is a slam-dunk case of an actor in a perfect-fit role. Scalia was alive and available to Gero when “The Originalist” debuted at Arena Stage in 2015, but the glory of Gero’s performance is how artfully it balances the actual man — an iron-willed conservative regarded by many on the left as heartless — with the comic demands of John Strand’s crowd-pleasing play.

The disarming laughs come early as Strand hands the stage to a Scalia who’s combative but charming as he lectures on law and parries with the feisty young liberal who will be his foil throughout the evening. “The Originalist” demands that you like Scalia: Then maybe, just maybe, you’ll hear his arguments. Gero woos the crowd beautifully with a virtuosic blend of bluster, intellect and devastating wit.

Strand’s play has been a hit for Arena, where it’s now playing on the larger Kreeger stage after premiering in the 200-seat Kogod Cradle two years ago (and then playing several theaters across the country). Director Molly Smith hasn’t substantially restaged the piece: It’s still furnished with little beyond Scalia’s imposing desk, and it still uses a thrust stage, though it’s cut back from the runway that jutted well into the Cradle’s seating.

Nor has Strand radically reworked a script that seemed implausible in its portrayal of Cat, the Harvard-trained African American clerk who so rudely claws at her boss. Looking again, it’s easier to see how much the play is wish fulfillment: Rather than being strictly realistic, Cat gives robust, unadulterated voice to Scalia’s critics.

They are loud and often crude, and so is she as she takes swing after swing at Scalia, starting with his views on affirmative action and Roe v. Wade.

The supporting roles have been recast, and Jade Wheeler is now Cat. Wheeler is quick, and she can be wry, but above all her Cat is determined. The script still softens as Cat battles the third and least persuasive character, Brad (a smug Brett Mack), a one-note neocon ninny of a clerk whom even Scalia can hardly stand. When Cat and Brad argue, it sounds like talking points being ticked off.

Their arguments don’t flow.

That’s the gap in the play, or at least in the performance (still). When Gero reasons as Scalia, you feel the force of the ideas, the bedrock of thought and of principle, even if you disagree. The mission of “The Originalist” is getting people to listen, and — at least with Gero so richly inhabiting Scalia — it may be that rare play of political ideas that can woo audiences in territory marked blue, red or purple. (It’s a pre-Trump play that doesn’t sound much different now; the rifts are the same, and all the points still land.)

Gero dexterously steers us through the legalese as Strand, whose body of work as a distinctly Washington writer may be undersung, eventually finds a plot in how Scalia handles his 2013 dissent in United States v. Windsor. That ruling invalidated parts of the Defense of Marriage Act and opened the door to same-sex marriage, which Scalia opposed in terms that some found unforgivable. It’s a well-chosen wedge as Strand asks about heart and scrapes hard to find human middle ground.

The way “The Originalist” works, you hang on every word from Scalia, from his bitterness at being passed over as chief justice to teaching Cat to fire a gun. Gero’s bearing is unimpeachable at every turn: This holds up as a great performance, commanding in case law and bull’s eye with feeling and wit. Scalia loses this showy comic drama’s big case, but he still walks away with the play.

The Originalist,by John Strand. Directed by Molly Smith. Set, Misha Kachman; costumes, Joseph P. Salasovich; lights, Colin K. Bills; sound design, Eric Shimelonis. About an hour and 45 minutes. Through July 30 at Arena Stage, 1101 Sixth St. SW. Tickets $41-$101. Call 202-488-3300 or visit arenastage.org.