After the private Capitol and White House tours, and the patriotic concert by the naval drum and bugle corps, and the one-man show by the guy wearing knickerbockers who sang "Yankee Doodle Dandy," there remained the matter of a farewell brunch aboard the Cherry Blossom. And about this grand finale Don Foley was very much concerned.

It was Day 2 of the rollicking constituent weekend organized by Foley's boss, Rep. Richard Gephardt (D-Mo.), for 125 folks from South St. Louis. In just 48 hours, the Gephardt Weekenders would be heading home, and Foley, the congressman's press secretary, wanted to be sure they left thinking about "upbeat Americana."

What he didn't want, Foley was telling Joyce Aboussie, Gephardt's campaign manager, was "what I call the politics of Jim Jones, you know, that 'let's drink the Kool-Aid' kind of downer." As he stood in the Capitol Rotunda Friday afternoon, Foley also seemed worried because Aboussie, who was in charge of Sunday's floating finale, was keeping her precise plans a closely guarded secret.

"It's going to be completely different from last year," she told him.

But this did not relax Foley. He liked last year's multimedia slide show on the river boat, he said. The one based on the Neil Diamond song, "Coming to America." The one that started with all the flashing pictures of happy constituents while the sound track thundered "God Bless America."

"Hey," Aboussie told him, smiling wryly, "trust me."

And well he should have. For if Don Foley had known what Joyce Aboussie had in store for Sunday morning -- if he had known about "The Battle Hymn of the Republic" and The Message from a Refusenik, his worries would have vanished like dust in the wind.

Dozens of congressmen invite their constituents to Washington each year, but suffice it to say that none of them gives Weekends like Dick Gephardt.

The 125 Gephardt constituents paid $850 each for the four-day trip. Some came to look inside the corridors of power. Some came to party. A few figured on lobbying their congressman eyeball to eyeball.

But mainly, they said, they came simply because they love Dick Gephardt, their red-haired, Eagle Scout, "new generation" Democratic representative -- a dark horse candidate for president in 1988 and an all-around standard-bearer of the American Way.

"I have a positive attitude and I think Americans generally have a positive attitude," says Gephardt, whose primped locks and boyish looks evoke Mark Alan Stamaty's cartoon character, Bob Forehead. "I think we need to feel good about ourselves. It's like a child. The most important thing you can give a child is a positive image of himself -- it's a self-fulfilling prophesy. It's the same with the country . . . "

He sounds as if he's plagiarizing the "It's morning in America" themes devised by President Reagan's political strategists -- but take it from Gephardt's Cub Scout den mother, Weekender Lucille Besch, that "he's always been that way." In Congress, Gephardt is best known for his quiet ascension to his party's No. 4 leadership slot in the House of Representatives, the chairmanship of the Democratic Caucus; for his coauthorship of the Bradley-Gephardt tax reform bill; and for his recently sharp protectionist rhetoric. But back in the old, established city neighborhoods of South St. Louis, his constituents are drawn to him for reasons altogether less prosaic.

"We feel like we're the guardians of middle-class America," explains Walter Roseburrough, a pipe fitter and Missouri union official who came on the trip. "We're lookin' big time. This man's got presidential capabilities. We've come to see what he's got to offer."

For starters, he had a big brass band.

As a heavy dusk settled on the Mall grounds Thursday evening, the Red Arrow tour buses filled with Gephardt's exhausted constituents arrived at the steps of the Lincoln Memorial. One by one, the junketeers were escorted by Naval Academy cadets in black dress uniforms into a large striped tent that had been erected on the lawn. At the canopied entrance stood Gephardt himself, flanked on the left by liberal Rep. Tom Downey (D-N.Y.), and on the right by fellow tax reformer Jack Kemp (R-N.Y.). Forty yards behind the tent, beneath the illuminated Washington Monument, the U.S. Naval Academy Drum and Bugle Corps stood at attention, their gold buttons gleaming in the spotlights.

"Hi! How are you? Long time no see!" Gephardt beamed, pumping hands like a farm boy milking cows.

"You must be dragging," an arriving Capitol Hill staffer told him, aware that Gephardt had been working late all week.

"Feel great! Everything's terrific!" the congressman smiled.

"What's he on?" the staffer asked incredulously.

Gephardt only laughed, but the question led to a discussion of the recently concluded baseball drug trial in Pittsburgh, then to the National League pennant race in which the St. Louis Cardinals are involved. The receiving line clogged while the congressman rhapsodized about Cardinals pitcher Joaquin Andujar.

Even Gephardt's fondest admirers concede that their man has at least one obvious character flaw-he likes baseball too much. "It gets in the way," says Don Foley. "Toward the end of the season, you start thinking that maybe it's a good thing that it's going to end."

Inside the tent, the crowd stood at attention for the national anthem. They were dressed unpretentiously, the men in dark suits and sports jackets, the women in pastel skirts and slacks and single-pearl earrings. The band strode toward the tent, blasting American marches and hymns. Then, inexplicably, it played what sounded like a Russian folk dance. No one complained.

"You're going to have fun this weekend!" Gephardt told the crowd when the music was finished. "You're going to learn things. You're going to learn about government, about Washington-that it isn't an imaginary place, it's a very real place with very real people."

Originally, the constituents had been told that "30 or 40" congressmen and senators would turn out to meet them, but when Gephardt made his introductions, he named less than 15, and some of them had already left. Jack Kemp had gone home to watch a football game on television.

Still, everyone seemed pleased.

"He's a very likable fellow," said Paul Miller, nodding approvingly at Gephardt, who was standing at the front of the tent, encircled by a bevy of Weekenders. Miller is a black businessman who does not actually live in Gephardt's district ("there are very few blacks in the district at all," he says), but who owns some stores in South St. Louis.

"He's probably everybody's example of the yuppie generation. He's a very clean-cut fellow."

Friday morning, it was time to go to school. The curriculum included taxes, the economy, the budget -- and above all, U.S.-Soviet relations.

The big Red Arrow buses took the bleary-eyed political travelers from the L'Enfant Plaza Hotel, where the constituents stayed, to Capitol Hill. By 9 a.m., they had convened in the Caucus Room of the Cannon House Office Building, where they would hear public policy lectures from a dozen congressional luminaries, including Kemp, Budget Committee Chairman William Gray (D-Pa.), Armed Services Committee Chairman Les Aspin (D-Wis.), and Energy and Commerce Committee Chairman John Dingell (D-Mich.).

More than half the speakers addressed defense issues. Aspin was first up on the topic, but just as he began to speak the House vote bell sounded, and all the other congressmen rushed from the room. Aspin said he would vote after his colleagues returned, and while they were away, he warned Gephardt's constituents about "the depth" of the Russian threat.

"These Soviets are a tough bunch of customers," he said confidingly. And he told the crowd to especially beware of liberal politicians who are "always making excuses" for aggressive Soviet behavior. At the same time, he said, they should be equally skeptical of conservatives who downplay the horrors of nuclear war.

Then Aspin's colleagues returned, and Downey, the young New York liberal, stepped to the podium. Unaware of Aspin's prologue, he launched immediately into a lecture about the history of Russian society and culture. It was important, he said, for Americans to try to understand the historical currents and events underlying the Soviet world view. Soviet "paranoia" about the United States, he argued, is at least partly attributable to the armed invasions the Russian people have had to endure over the centuries.

When "school" was recessed for lunch, the South St. Louis voters began to talk about the speeches they had heard. In a highly informal survey, more than 20 of them were asked which of the congressmen had impressed them most. (Gephardt himself was barred from consideration.) Surprisingly, the "guardians of middle-class America" named Downey -- "that little guy from New York" -- most often.

"He's so young, but he opens his mouth and you can't believe how intelligent he is," said Daphene Euston, a retired widow. "He was very impressive," chimed in Buzz Westfall, a government prosecutor in St. Louis County.

Finishing a clean second was Kemp, who resides at least as far to the political right as Downey does to the left, and whose typically fervent speech about hope and a conservative "opportunity society" drew the loudest and longest applause from the overwhelmingly Democratic audience.

Some of them, of course, came to town knowing what they might accomplish here.

There was the clan of AFL-CIO officials from St. Louis and Kansas City who, for the price of their $850 tickets, hoped to make some serious political judgments about Gephardt and to bend his ear about exempting fringe benefits from taxation in the Bradley-Gephardt tax reform bill. ("I'm always working," said Duke McVey, president of the Missouri State Labor Council. "That's my job.") There was the elderly lady looking for help for her husband, who was having trouble with the Veterans Administration. And then there was Edward Richardson, a retired boat dealer, who saw his chance and took it.

The moment came on the steps of the Capitol Friday afternoon, under a hot sun, after a demanding tour devoted as much to staircases as to historical sights. Gephardt was standing before the assembled group, looking very much like a tour guide, craning his neck over his constituents in the vain hope that he might spot the stragglers who were holding things up.

Out of the pack stepped Richardson, smiling. He told Gephardt about these lots of land he'd owned in South St. Louis, which he'd sold to the federal government, and for which he had yet to be paid.

Distracted, a little confused, Gephardt looked down at him and asked, "Why didn't you get paid?"

"That's what I'm asking you," Richardson replied.

It was a test of any congressman's temper -- the heat, the question, the demand. And Gephardt, no doubt trying to think positively, passed. "Oh," he said. "I don't know the answer but I'll try to find out."

At Friday night's dinner at the Gephardt home in Great Falls, the congressman's wife Jane put in her longest appearance of the four-day fete. She grew up in a small Nebraska town and, she says, "I'm basically kind of a shy person." Jane says she shares her husband's exuberantly positive attitude about life in America but concedes that Dick "is probably more positive than I am in some ways. After living with him for 19 years, it's kind of rubbed off." At the party she hosted under a tent in her back yard, a character actor dressed in a Revolutionary War costume told 18th-century jokes and led the Weekenders through a few patriotic choruses.

On Saturday the buses rolled once more, this time to lunch at the old Iranian embassy, where, as campaign manager Aboussie put it, the group got to see "some of the shah's old things." There was a private tour of the White House, and a quiet dinner-dance honoring Sen. Thomas Eagleton (D-Mo.), and increasingly, a chance for the Missourians to reflect on what they had learned about Washington, and about their congressman, Dick Gephardt.

"It wasn't as big and complicated as I thought it would be," said Nina Buist. "The rooms weren't as big as I thought."

"Congress was more streamlined and effective than what I had perceived from the hinterlands," said her husband Gene, who owns a mining equipment company in St. Louis.

"As I told my husband," Mrs. Buist added, "I almost feel like volunteering to work for Dick Gephardt because he's so inspiring."

At the end, the sun peeked through the clouds -- how could it not?

Around noon yesterday, after brunch and a Potomac cruise that featured mostly the sights and sounds of National Airport, the constituents traipsed down into the Cherry Blossom's main-deck ballroom, where Aboussie had been hiding behind closed doors for the previous hour, putting the final touches on the weekend's denouement.

They fixed their red, white and blue Gephardt campaign name tags for the last time and sat close together on deck chairs.

"Well, we're at the finale point," their congressman told them, smiling widely. "You've been a great, great group to have here." Then he introduced his staff. Everyone applauded. He introduced his three blonde, freckle-faced children, and everyone clapped some more.

"You, too, are an important part of my ability to succeed," Gephardt told his constituents. "Without your support, without your understanding, without your help, I can't do the kind of job that I think you want done." The congressman went on to mention some upcoming campaign fund-raising events in St. Louis, and said he hoped everyone in the room would be able to help out.

Then the lights went down, the projectors glowed, the music started and the show began.

The first picture was of an American flag. The second picture was of a Russian flag. It went back and forth -- a picture of Red Square, then one of the Washington Monument; a shot of the Kremlin, followed by one of the U.S. Capitol lit up in the night sky. A sorrowful piano solo swelled on the sound track.

Gephardt's voice came on, and over pictures depicting life in the Soviet Union -- posters of Lenin, dissidents behind bars, Siberian labor camps -- he began to tell a story. He said that a couple of years ago, he traveled to Russia with his wife. There he met a refusnik, a mathematics professor at Moscow University who had been arrested for teaching Hebrew in his home. He told of the professor's harsh treatment: three years in a labor camp, permanent separation from his family, demotion to a job shoveling coal.

Gephardt described his private meeting with the professor. He said that the professor told him, "I hope you'll go back to America and tell your people that to me, and millions of people like me, America represents freedom."

As he was leaving the apartment, the congressman continued, "the man put a note in my pocket, and when we were in the car speeding back to the American embassy, I pulled it out. And there, in nearly illegible and difficult English, he had written these words: 'Dear Mr. Congressman, please don't forget us.' "

A breathless pause followed. Then the sound track boomed a full choral version of "Battle Hymn of the Republic." Next, pictures of the constituents during their Gephardt Weekend came on the screen -- shots of them at the Lincoln Memorial, the Capitol, the White House. The music changed to the theme from the 1984 Los Angeles Olympics, then to "This Land Is Your Land."

When it was over, they stood and applauded, some of them teary-eyed, others smiling broadly, all of them astounded and exhilarated by what they had seen and heard. "It's not the show I would have done for people in Washington," Foley said, "but Joyce knows her market."

Then the Cherry Blossom docked, and the buses came again, and they rolled to the airport to fly the Weekenders home.