On the morning after the night that Robert Bauman watched his once promising political career dissolve in a narrow defeat, he was forced to face once more the very problem that had helped drive him from the U.S. House of Representitives.

Hours after giving a humbling and heartful concession speech to supporters here, Bauman traveled to Baltimore to appear before a federal grand jury investigating James E. Regina, the man accused of trying to blackmail Bauman with threats to make their alleged homosexual relationship public. Late today, the grand jury indicted Regina on charges of mailing a threatening communication to Bauman and attempting to obstruct justice.

Bauman's grand jury appearance was a grim epilogue to a drama that began Oct. 3 in another courthouse with revelations of Bauman's troubled sex life and ended early this morning as Bauman climbed atop a mahogany chair in Easton's elegant Tidewater Inn to concede the election to his opponent, Democrat Roy Dyson.

But the nationally known conservative figure, who proclaims himself a "new Bob Bauman," did not act like a beaten politician today.

"I feel fine. I feel great," he said from his prime white farmhouse on a country road here. "Politics is not the most important thing in my life anymore. I couldn't have said that a couple years ago . . . or even a few months ago, but there really is a new Bob Bauman."

The old Bob Bauman, acknowledged parliamentary wizard and verbal sharpshooter of the Republican right, was riding high in Congress a few months ago, his oratorical aim directed at colleagues who had drawn his scorn, and his eye on a position as the next minority whip.

But on Oct. 3 all that changed. Bauman entered a Washington courtroom and agreed to undergo rehibilitation rather than face trial on a charge that he had solicited sex from a teen-aged boy. Days later, at an emotional press conference, he admitted to the "twin compulsions" of alcoholism and "homosexual tendencies." On the same day Regina, a former bartender at one of Washington's gay bars, was charged in the attempted extortion plot.

Those relevations turned his Democratic opponent, Maryland State Del. Roy Dyson from determined underdog to frontrunner, and early this morning the results confirmed that turnabout and showed Bauman with only 48 percent of the vote -- 88,736 to Dyson's 96,394 -- in the district he once had a lock on.

As the returns, agonizinly delayed by a computer problem in one key county, finally confirmed his loss, a surprisinly feisty Bauman swept into his traditional election night gathering at the Tidewater Inn to tell supporters that though he has lost the election, he and his wife, Carol, were "at peace with ourselves and with God."

In one of the few somber notes in his speech, Bauman told supporters, a few of them weeping, "I can say, contrary to various estimates in the press, that I too am human and Carol and I and our children have suffered greatly as a result of my shortcomings. The cause of their suffering will always be a painful memory that I will take with me to my grave."

As his teen-age daughter Jenie held him tightly around the waist, Bauman told his supporters that they would "live to fight again another day." And in a characteristic parting shot at the press, he said with a grin, "who knows, you may have me to kick around again some time."

Though many of his saddened supporters speculated that this meant an attempt at a political comeback in 1982, Bauman today was looking no further ahead than the lame duck session of Congress.

"On Nov. 12, I'll be back on the Hill working to protect the American people in the last waning days of the Carter administration," Bauman buoyantly asserted.

And would the Carter administration be trying to put something over on the American people in those waning days? he was asked.

"Not as long as I'm there," he vowed.

Friends here wonder what Bauman will do next, speculating that he could practice law or even serve in the administration of Ronald Reagan.

Asked about both those possibilities, Bauman answered simply: "I don't have any idea what I'll be doing."

While the defeated incumbent wondered about his future, Dyson ate a steak-and-eggs breakfast and vowed to begin his congressional homework with a whirlwind tour of the district today.

"The district will be my first priority," he said. "I know the Republican will be watching me. I have no doubt that this district will be earmarked in 1982 for my defeat. I'll be working very hard to keep my seat."

Here in Easton one man said that defeat "was just what Bob Bauman deserved," but most people used words like "travesty" and "unfair" and "sick" to describe their tarnished conservative hero's loss.

After returning from Baltimore, Bauman spent a quiet day at home with his family. His local office, above a bank in Goldsborogh Street, remained closed. And two of the congressman's closest aides could be seen at noon silently carrying a giant red-and-white "Bob Bauman for Congress" sign into a back room at the local GOP headquarters.