Eunice is nothing if not the centerpiece of "Eunice," the Carol Burnett special on CBS tonight at 9:30. Burnett's husband, Joe Hamilton, produced the program, every scene features Burnett, and the comedy-drama has been constructed as a veritable Macy's window of histrionics by the star.

In spite of all that, it's really Vicki Lawrence's two-fisted portrayal of Eunice's relentlessly cantankerous mother that one is drawn to on the program, a 90-minute special at 9:30 on Channel 9. And so it seems particularly churlish, and dramatically self-destructive, for the writers to kill Mama off in act four, mainly in the interests of handing Eunice another dramatic thunderbolt to wrestle with.

It does help develop the character of Eunice, but this is a character that can't take that much development. In the Eunice sketches on the old, dearly beloved "Carol Burnett Show," Burnett and company played for laughs the kind of lowbrow folk types who had been played for high drama on the stage. Eunice, her gabby Mama and her witless, feckless husband always seemed like Tennessee Williams characters that Tennessee Williams would never have bothered with. It made for, and still makes for, strangely compelling TV.

Writers Dick Clair and Jenna McMahon put Eunice through the mill and the wringer in this new version, divided into four acts that each represents a year in Eunice's dreary and pointless life--1955, 1965, 1973 and 1978. Essentially they have written a very good bad play. The slightly frightening fun of Eunice was always the combustion, however--the ceaseless shouting conflict among the characters, the bathos that reached a fever pitch and yet kept going even beyond that. By having husband Ed disappear in act three and by bumping off Mama in act four, the writers have bequeathed lock, stock and spotlight to Eunice, who deserves less.

Harvey Korman, as Ed, is an immaculate study in compromise and carefully preserved simple-mindedness. Betty White's Ellen, Eunice's sister, is another polished gem. Ken Berry capably plays son Phillip, the family's lone level head, who goes off to write novels and win Pulitzers and returns home only to find politics as usual. Lawrence's Mama may be the most fully realized of the lot, however, and it's an odd pleasure to hear her snapping out her what-the-hells again, and planning to "swing by the cemetery," and bouncing merciless put-downs off Eunice.

"Face it, Eunice, you missed the boat," sums up Mama to Eunice in act three. Eunice's father, the man who dared to marry this Great Depression, "Carl Harper," is never seen. He spends the first act in the bathroom (writer Clair handles his voice) and is dead by 1963. Hence the plan to swing by the cemetery. Eunice is full of plans, of course--plans to be famous, plans to shed the small-town life--and totally lacks the will or talent to carry them off. Burnett gives her dimension and even dignity, but she was still more at home in sketches than in an over-reacher like this.