The 12-year-long administration of D.C. Mayor Marion Barry is in its final days, but in a sparsely attended trial now underway on the sixth floor of U.S. District Court here, federal prosecutors are once more taking aim at it.

The charges: contract steering and bribery. The targets: an old friend of the mayor's, John B. Clyburn, and a former high-ranking official of the Department of Housing and Urban Development, James E. Baugh.

It was a case that began in 1986 when a much ballyhooed federal probe of alleged widespread contracting irregularities in the Barry administration first became public. But the subtext in U.S. v. Clyburn and Baugh is a complex weave of racial politics, 1980s attitudes about affirmative action and the sometimes blurred line between networking and bribery.

Closing arguments are expected tomorrow, with the mayor's attorney, R. Kenneth Mundy, representing Baugh and local criminal defense lawyer Thomas Dyson representing Clyburn. Dyson should find his role familiar: This is the second time this year that he has defended Clyburn in federal court on charges of using his influence with Barry administration officials to subvert the city's contracting procedures.

In the first trial, Clyburn was charged along with former D.C. Department of Human Services head David E. Rivers with steering about $2 million in human services contracts to Clyburn's computer firm and a small circle of Clyburn's friends. Clyburn and Rivers were acquitted in July after a three-month trial.

That case featured an undercover FBI agent posing as a good-old-boy Atlanta businessman looking for a minority "front," detailed explanations of department contracting procedures and an alleged payoff to Rivers of a pair of snakeskin cowboy boots. This time, there are no undercover agents and the alleged quid pro quo is clearer: a $400,000 HUD contract to Clyburn, in exchange for Clyburn's help in getting Baugh's wife, Veatrice, a start in her own business and a $45,000 contract from the D.C. government.

And quid pro quo equals crime, Assistant U.S. Attorney Blanche Bruce told the jury during her opening statement last month.

"There's a phrase we all use and know: 'Scratch my back and I'll scratch yours.' " But, she added, "When you decide to scratch the back of a public official, and he knows you're trying to influence him, you've committed bribery."

Clyburn and Baugh have a different version. Asked by Dyson in court last week to explain his use of the term "quid pro quo," Clyburn matter-of-factly shrugged off any sinister insinuation.

"I tend to use it interchangeably with 'networking,' " he said.

During a break in the trial last week, Baugh said that he was only trying to ensure that a deserving black contractor got his share of HUD business. If sometimes he had to go to great lengths to even the odds, Baugh said, that was the only way businesses such as Clyburn's could compete for federal contracts during a political era hostile to affirmative action.

So opposed were some of the Reagan administration "true believers" at HUD to the idea of minority set-asides, Baugh testified, that he developed his own term for them: buzzards.

"It was the same old story: 'They're not experienced, they can't do the work,' " he said later in an interview. "After awhile, it becomes blatantly racist."

What's unusual in this case is that the facts, consisting mostly of conversations wiretapped by the FBI from Clyburn's office phone, largely are undisputed. What's at stake is their interpretation.

The government's interpretation is straightforward: For different reasons, Clyburn and Baugh were both looking for money. Clyburn wanted to enlarge his business, Decisions Information Systems Corp., which did consulting work for the D.C. and federal governments. Baugh's motive, they say, was augmenting his income.

That, prosecutors say, Baugh hoped to do through his wife, an entrepreneur looking for a business. In early 1985, according to prosecutors, an Atlanta businessman Baugh knew, Bobby Smith, mentioned the possibility of acquiring a D.C. distributor for a product he was marketing, a line of janitorial supplies. Baugh said his wife might be interested.

Smith, who was part of Clyburn's business network, introduced Veatrice Baugh to Clyburn in early 1986. As he had done before for other struggling black businessmen, Clyburn gave Veatrice Baugh rent-free office space and marketing advice. When the janitorial supply distributorship fell through, prosecutors say, he also gave her an entree into D.C. government that helped her get a contract with the Department of Employee Services.

All the time, according to the wiretaps, Clyburn was angling through James Baugh for a HUD contract to do computer work for the public housing authority in Columbus, Ohio. In an FBI wiretap from July 1986, Clyburn told one of his employees, DISC President Don Campbell, that the pending HUD contract was linked to his help to Veatrice Baugh.

James Baugh, Clyburn said, "has been kind of quietly doing his number, and not saying anything. He sent a couple of messages to me through his wife. The big issue with him is he wants us to keep doing what we can for her."

But Clyburn testified last week that he agreed to help Veatrice Baugh before he knew the identity of her husband, whom he met in person for the first time in July 1986.

Attempting to defuse one of the prosecution's main weapons, Clyburn's attorney, Dyson, pressed him on the point. Wasn't it true, Dyson asked, that Clyburn knew it would please James Baugh a lot to know that Clyburn had been so helpful to his wife?

"I certainly wasn't going to mistreat her," Clyburn replied with a grin. The jury chuckled.