The government's case against Rep. Daniel J. Flood (D-Pa.) ended in a mistrial yesterday when jurors failed to reach a verdict after 12 hours of deliberation.

Reliable sources, including a juror, said that a lone holdout prevented the jury from finding Flood guilty on all but two of the 11 felony charges.

Government lawyers would not say whether they would recommend a new trial for the 75-year-old congressman, who was charged with bribery, conspiracy and perjury.

Most observers believe that Flood's frail health and his fading power as a congressman may be decisive factors weighing against a second trial.

Flood, who appeared withdrawn and passive through much of the trial, managed a smile and a comment as he walked haltingly to the microphones after the mistrial was declared.

"I regret that the jury was unable to reach a unanimous verdict of acquittal," he said. "At this very moment, I maintain my innocence of any wrongdoing in the charges considered against me."

Then the once theatrically flamboyant and powerful congressman, known for his waxed handlebar moustache and his cape, was escorted to a car by aides who supported him as he limped away.

Flood was charged with 11 counts revolving around a series of six largely unrelated bribes worth about $54,000 he allegedly received from people seeking his help in securing government favors.Among the alleged bribe payers were a foundation director who wanted government grants, a housing developer who wanted federal financing, a trade school operator seeking accreditation and a New York rabbi searching for federal funds to retrain Soviet Jewish immigrants.

The government had no single witness who could reliably tie everything together, and had to rely on the cumulative effect of a string of witnesses who said they had placed money in Flood's hands.

The defense was able to raise numerous questions about the credibility of the prosecution testimony, both by pointing out repeated discrepancies in a confusing tangle of times and places and by focusing on the widespread grants of immunity under which many of the witnesses testified.

The trial lasted 15 days. It went to the jury on Thursday, and it was soon clear that the jurors were deadlocked and somewhat confused about the process confronting them.

The first report to the judge of a deadlock was unusually early -- three hours into the deliberations Friday. Judge Oliver Gasch told jurors to go back and try harder. But about three hours later, the jury again reported a deadlock with "no evidence that we will ever be about to reach a verdict."

Gasch reminded them that they could reach a "partial verdict" -- guilty or not guilty on one or more of the 11 counts. The jurors then sent another note saying they did not understand what Gasch meant by a "partial verdict."

At 3.15 p.m. yesterday, the foreman said he was "sorry to say that at this time it is impossible for this jury to reach a verdict." A half hour later Gasch ended it all.

"With the utmost reluctance," he said, "I am forced to declare a mistrial." Some jurors cried as they left the room, apparently drained by the experience. One woman turned to a prosecutor and said, "I'm sorry."

Sources said last night that William Cash was the lone holdout who prevented the jury from finding Flood guilty on all but 2 of the 11 felony charges against him.

Juror Johnnie Lyles, 52, a data processor at George Washington University, said in a phone interview that Cash refused even to discuss the merits of the case. She quoted Cash as saying: "I know he's guilty on some of the charges, but I'll never vote to send an old man to jail."

Cash could not be reached for comment.Lyles said, "I sat next to him. It was my duty to keep punching him to keep him awake... All those old men slept through it."

The trial produced an intriguing cast of characters and a colorful web of Washington wheeling and dealing.

Stephen B. Elko, 51, former administrative aide to Flood, who testified that he orchestrated the alleged conspiracy for his boss. He said Flood advised him about Capitol Hill: "Remember, Steve, this is a business. If you handle this the way I know you can, the rewards will be there for both of us."

By his own testmony, Elko heeded the words enthusiastically. On one occasion, he nearly drove off the highway as a bribe payer in the back seat handed him an envelope stuffed with cash. "Is that for me? Is that for me?" he repeated, craning his neck to see the white envelope, according to testimony.

Deryl Fleming, a hard-drinking, wisecracking Washington lobbyist known as "Corn Flakes" because he once represented the Kellogg Co. who testified that he gave Flood a thousand dollar cash payoff on behalf of the West Coast Trade Schools. Fleming, who said he used to consume up to 30 bourbons in a single day, said he didn't even have to look inside the white envelopes passed around in front of him to know cash was inside because he had "15 years experience watching money change hands" in Washington.

Rabbi Leib Pinter, 35, of Brooklyn, who told of taking cash from the B'Nai Torah congregation bazaar and tea fund to buy Flood's help in getting federal funds for a manpower project. "'Keep up the good work, Murphy,'" was how Flood once thanked him, according to Pinter, who is now serving a prison term in connection with the case.

"Keep up the good work, Murphy," a Flood aide later testified, was a salutation foten used by the congressman for anyone who wasn't Irish.

Dr. Murdock Head, a prominent George Washington University physician who allegedly hustled federal grants for the Virginia-based Airlie Foudation by making cash payments to Elko and Flood. According to testimony, Head would generate cash by having phony expense vouchers created for the foundation. After having the currency wiped clean of fingerprints, he would pick it up with facial tissue and hand it over, a witness said. Head has denied all wrongdoing.

Everyone seemed to have his own way of Describing the alleged bribe money. To Elko it was "long underwear to keep the congressman warm." For Fleming, it was an "insurance policy." For the rabbi, the lump sum Elko asked him to pay was "one big nut" to take care of everything.

In the face of such testimony, Flood's lawyer, Axel Kleiboemer, relied heavily on creating a favorable image for his client, independent of the allegations under consideration.

Everyone -- including prosecution witnesses -- seemed to agree that Flood was a good congressman. He had a remarkable attendance record on the floor. He was unstinting in his concern for constituents, keeping his door open at all times for anyone to see him and traveling every weekend to his Pennsylvania district for a grueling round of civic meetings.

When Hurricane Agnes devastated Wilkes-Barre in 1972, he set up a "command post" at a Naval Reserve armory and took charge of relief operations.

"He goes home each night," Kleiboemer told the jury in summation. "He rarely goes out to dinner except on his anniversary. No Jockey Club for him."

So busy was he that he gave Elko a free hand to run his office and his personal financial affairs, according to testimony. Flood "handed over his life" to Elko- Kleiboemer said, and "Elko looked at this frail old man and said, 'Let me do it.' Elko was allowed to sign his checks and his letters and the congressman took whatever recommendations he made."

According to testimony, Elko used this authority to solicit bribes and to send letters, under Flood's name, to various federal agencies on behalf of the bribe payers.

Flood's lawyers contended that Elko never included the congressman in his scheme except to set him up periodically in such a way that he would accept some money in the belief that it was an innocent honorarium or campaign contribution.

According to Elko, however, Flood encouraged the scheme, occasionally demanded larger payoffs, and once told Elko to "get all you can while you can get it."