Under the nightclub spotlight, Diane Miller Warren is crooning a musical rendition of the Virginia legislature's year-long fight over redistricting. To the tune of Johnny Cash's "I Walk the Line," she sings:

"So what if the ACLU's going to sue?

"So what if the NAACP is upset, too?

"So what if it's going to cost $1 million before it's through?

"Save our behinds when we draw those lines."

The crowd of legislators roars its approval; the mini-skirted waitresses at Tony's Supper Club smile appreciatively over their trays of beer and bourbon, and another night's revelry in the state capital is under way.

Legislators here are fond of talking about how hard they work on the state's business--how difficult it is to get up for early morning committee meetings, to sit through hours of floor debates, to wade through stacks of obscure legislation.

What they don't like to talk about, at least publicly, is the somewhat less grueling stream of cocktail parties, dances, fund-raisers and dinners that keep their social calendars filled for the legislature's 60-day session. If it isn't one bash, it's another: shucked oysters and beer with the state's beer wholesalers, smoked salmon and crabmeat at the Virginia Museum of Fine Art, bluegrass music with the Republicans and recycled stump speeches with the Democrats.

For those legislators who would rather go back to their hotel rooms and curl up with a good tax bill, all of these celebrations can get to be a bit tiresome. For the rest, parties such as the annual "Legislative Follies" held last week at Tony's, are among the high points of the law-making season--even more fun, perhaps, than the pork-barrel amendments they've tucked into the state's $13.2-billion biennial budget.

Where else could a roomful of legislators hear House Majority Leader Thomas Moss (D-Norfolk) sing "Danny Boy" in an earnestly sentimental Irish tenor? Where else could they see a star-struck legislative aide, clad in the slinkiest of white disco dresses, belt out her version of "Hot Stuff?"

And where else could they see Del. Theodore (Teddy) Morrison, a Newport News Democrat considered one of the House's rising stars, deliver his impressions of the charms of young womanhood? (Example: "My friends all told me she was a 10, but I could never figure out why. She always charged me 20.")

For two years in a row, Diane Warren and her free-wheeling political satire have been the hit of the session's annual talent show. Now the 38-year-old sister of two Republican delegates is lampooning GOP be te noire Sen. Nathan H. Miller, the former candidate for lieutenant governor whose absence from the Senate one recent day killed the Equal Rights Amendment.

Miller, who lost the election last fall following conflict-of-interest charges concerning his work for the state's electrical cooperatives, is nowhere to be seen when Warren begins singing (to the tune of "Leaving on a Jet Plane"):

"Oh, the tension's high; it's a big, big day,

"They're going to vote on ERA,

"And even Lynda Bird is looking on.

"But Nathan's on a jet plane. He's front page news again.

"Nathan must have co-ops on his mind."

There's more to the parties, legislators insist, than competing for prizes at the First Annual Legislative Invitational Disco Contest (won last week by a freshman Republican from Altavista) or lining up dinner partners among the multitude of legislative aides.

For the lobbyists--be they bankers, teachers, builders or health-care agents--entertaining the legislators is part of their business.

For the lawmakers, the Richmond scene is beginning to resemble those last carefree days at the end of a long ocean cruise. As the session winds down, coalitions that have formed and broken up are back together, waiting in line for another plateful of fried chicken, egg rolls and bacon-wrapped chicken livers. The "in" jokes are more "in" than ever, and the gang is getting maudlin long before the third bourbon-and-water arrives.

In the front row, Gov. Charles S. Robb, perhaps the most party-going governor this staid capital has seen, is laughing uproariously at Warren's musical "Chuck Roast" (to the tune of "What You Going to do When the Rent Comes Around"):

"Hey Governor Charles Spittal Robb,

"What you going to do now you've got this job?

"Can't you hear the Democratic leaders bark?

"They say you're leaving them out in the dark.

"I know you're anxious for 1988,

"I hear Lynda's measuring the White House drapes.

"Hey, Governor Charles Spittal Robb,

"What are you going to do now that you finally have a job?"