On Day One of waiting for a federal jury to decide whether he is guilty of conspiracy, drug possession and perjury, D.C. Mayor Marion Barry never made it to the courthouse.

At 7:30 a.m., he was at the Randall Heights tennis courts in Northwest Washington, where he played a Washington Post reporter for about an hour (no scorekeeping allowed). Then he lunched at the American City Diner with owner and friend Jeffrey N. Gildenhorn. Then he went to Catholic University for a Marion Barry Youth Leadership Institute gathering to hear student candidates make their speeches. He got a standing ovation.

"We thank you! We appreciate you! We love you! We support you! We want you to come back!" chanted the crowd of about 300 students, prompted by one of their leaders, before spontaneously breaking into, "Bar-ry! Bar-ry! Bar-ry!"

For a man facing a possible perjury conviction, and jail time, how does this feel?

"Fantastic," Barry said, grinning widely. It is his standard answer -- and, as usual, it sheds no light on what enables him to act as if having the United States government on his case were nothing more serious than another campaign.

From the beginning, Barry has acted as if the trial were a campaign event -- entering the courtroom each morning through a side door, smiling at reporters, greeting some by name, bending over to kiss and hug political supporters.

One day recently the mayor was explaining to reporters that the African kente cloth scarf he wears around his neck was a symbolic expression of black solidarity against white oppression.

"It's fight-the-power day," he said, and seemed inclined to elaborate. But just then Deputy Marshal Al Crews showed up to take him firmly by his arm and lead him to his seat. Power 1, Barry 0.

Barry is a complex political creature, and getting past his public facade takes stealth and art and patience. On any given day, what's on view may be playful, or proud or pugnacious -- or all three.

"You know," Barry told a table full of reporters in the courthouse cafeteria one day recently, "you guys have made me international." He stopped for a moment, struck by a thought. "Interplanetary, really. Bet they're watchin' on Mars. 'Bout five eyes." He leaned foward, making goggles with his fingers, his idea of what a five-eyed Martian looks like. "You guys have made me a folk hero," he said.

Then, the temperature abruptly changed. After he leaves office, Barry told the reporters, he plans to protect his privacy.

"Being a public figure is like being radioactive," one reporter told him. "There's a half-life."

"Just try it," he said, feigning an uppercut. "Strong right." He was not smiling.

On other days, the mayor has seemed imperious, immune to the opinions of those around him. The day, for instance, that Linda Creque Maynard testified dramatically that Barry forced her to have sex against her will in the Virgin Islands in 1988, there was a kind of palpable dismay in the press corps. Some reporters said they found it hard to meet his eyes.

The defense later called Charles Lewis, a prosecution witness, to cast doubt on Maynard's story. Barry has vigorously denied Maynard's allegation. But at the time, if the story of forced sex bothered the mayor, it did not show.

Barry's lawyer, R. Kenneth Mundy, was not surprised.

"Some people are built for the battlefield," Mundy said.

Barry himself was cornered by a reporter a day or so later in an unusually subdued mood at Joe & Mo's. The occasion was the celebration of the acquittal of D.C. contractor John B. Clyburn on charges of contract-steering.

Amid the back-slapping, Barry sat at the bar, nursing a glass of iced tea, next to his old friend Ivanhoe Donaldson, himself a veteran of the federal courts. (Once a deputy mayor, he served three years in prison for defrauding the city of $190,000.)

"I'm the only expert on how Marion Barry is holding up," Barry said, as Donaldson listened. To understand why he bears himself so proudly no matter what, he said, "you have to understand the Afro-American psyche."

"So, are you afraid?" he was asked.

"Depends on what day of the week you're talking about," Barry replied, his eyes elsewhere. Donaldson could contain himself no more.

"What do you want him to do?" he asked the reporter. "Blubber?"

Mary Cox, a lawyer and staunch Barry supporter, said she understands what Barry means.

"The {Afro-American} male is much different" from Caucasian men, she said. "They carry themselves under the most unusual pressure . . . . Sometimes I think {the public} wants him to look like Jim Bakker," shedding phony tears. "But you're not going to see that . . . . What you see is the real deal."

But sometimes the strain shows. In his pep talk to the students at the Youth Leadership Institute, Barry quoted poet Langston Hughes.

Echoing the advice the work-worn mother gave to her son in a Hughes poem, Barry told the young people, "Life for me ain't been no crystal stair."

Staff writers Barton Gellman, R.H. Melton and Michael York contributed to this report.