A three-member House panel has begun looking into the election of Richard A. Tonry, who could become the first House member to be unseated because of a disputed primatry race.

Tonry, a Louisiana Democrat, occupies the seat that was held for the last 35 years by Rep. F. Edward Hebert, former chairman of the Armed Services Committee.

Tonry's hold on that seat is in doiubt as the result of a dispute arising from the Oct. 2 Democratic primary runoff election in Louisiana's 1st District.

Tonry won by 184 votes. But his opponent, former New Orleans City Councilman James A. Moreau, immediately petitioned the state district court to overturn the election results on the ground the contest was won by "widespread vote fraud."

A federal grand jury investigation has produced 23 indictments charging that more than 400 votes were falsified by election commissioners belonging to a political faction that supported Tonry. The grand jury also indicted Tonry associate Donald J. Zimmer on charges he tried to cover up a $32,000 illegal contribution to Tonry's campaign.

The vote-fraud case has been heard by the state district, appeals and supreme courts. Only the Louisiana favor, saying Oct. 21 that it found at Court of Appeals ruled in Moreau's nleast 358 fraudulent votes cast in the runoff.

The appeals court said the election results should be overturned, even though it could not ba determined who benefited from the disputed votes. The state supreme court took exception to that ruling, however, and on a 5-to-2 vote said that the election results could not be voided without knowing who was helped by the disputed ballots.

The case is being studied by the federal grand jury in New Orleans, the Fifth U. S. Circuit Court of Appeals in New Orleans which is trying to decide whether the matter should be left to Congress - and the ad-Hoc three-member House panel, an adjunct of the House Administration Committee.

Six House panels soon will begin looking into the contested elections of Reps. William Clay (D-Mo.), Richard Kelly (R-Fla.), Carl D. Pursell (R-Mich.), Robert A. Gammage (D-Tex.), Abner J. Mikva (D-Ill.) and Robert L. Leggett (D-Calif.).

Only the Tonry and Clay cases involve primary races. The others concern general-election challenges.

A spokesman for the House Administration Committee, which is responsible for checking contested House races, said the committee has rarely reviewed a challenge involving a primary election. And as far as anyone can remember, the House has never unseated a member because of a disputed primary race, the spokesman said.

However, the grand jury indictments charging vote fraud in the Tonry case present an unusual complication. If they are unheld in court, Tonry's runoff election could be overturned - an action that would, in effect, nullify his nearly 5,000-vote victory over his Republican opponent in the Nov. 2 general election.

"There is just no chance that if these men (the indicted commissioners) get convicted of passing those fraudulent votes that Congress will not overturn the election," said Gibson Tucker, one of Moreau's lawyers.

"I can prove, and I believe that the U.S. attorney (Gerald Gallinghouse) can prove, that these votes were falsified in favor of Tonry," Tucker said. "You can't say that these . . . commissioners just decided to go out and commit vote fraud together. They had to have a motive."

But Rep. Mendel J. Davis (D-S.C.), chairman of the panel looking into the vote-fraud angle of the Tonry case, said yesterday, it would be premature to say the new congressman definitely would be ousted if his supporters are convicted of vote fraud.

"The indictments are for the election commissioners, not Tonry," Davis said. "Tonry is the man whose qualifications we have to check . . . You've got to invalidate the election by proving that the fraudulent votes were cast for Tonry. And that cannot just be a presumption, which makes it sticky.

Tonry is a self-described "political novice" who served one month in the Louisiana legislature before seeking federal office. He is 41 and a successful lawyer in Chalmette, La., in his native St. Bernard Parish (county). He is regarded as a moderate-to-liberal who is a strong supporter of labor unions.

By his own account, he is not supposed to be in Congress now. Out of a field of six candidates in the state's first Democratic primary in August, he was picked to finish fourth or fifth. Instead, he finished a distant second, tallying 18,888 votes to Moreau's 37,646 - difference of 18,758 ballots.

The local news media and political pundits predicted that Moreau, 62, who served two years in the state legislature and 10 years on the New Orleans City Council, would win the runoff by a landslide. But Tonry won by a vote of 48,789 to 48,605 - a 184-vote difference.

In the traditionally Democratic 1st District, the Democratic primary winner usually is assured easy victory over the opposition in the general election. Tonry won, but by a disappointing 4,973-vote margin - 61,652 votes to 56,679 - over an equally inexperienced politician, New Orleans lawyer Robert Livingston.

The 1st District is composed of four parishes - Orleans, Tammany, St. Bernard and Plaquemines. The most famous are St. Bernard and Plaquemines, tow Mississippi River delta communities whose politics for decades has been controlled by powerful local judges and parish sheriffs. Both parishes also are legendary reservoirs of what has lately come to be called "voting irregularities."

Tonry was backed by a St. Bernard Parish faction led by Sheriff John (Jack) Rowley. Nine of Rowley's deputies were charged in the federal vote-fraud indictments.

Moreau was backed by heirs of the late Judge leander Perez, who gained national notice because of his segregationist stands and whose heirs wield considerable political infuence in the district.

Tonry admits that some votes were falsified in the election, probably in his favor. "I think some have been proved," he said.

But, he quickly adds: "I'm realistic enough to know that there was vote fraud committed on the other side also, and I sincerely believe that there was much more vote fraud on the other side that is not being investigated."

Tonry claims his supporters have documented 1,500 "voting irregularities" attributable to Moreau's backers. But he said he took the advice of his attorneys and decided not be bring charges.

"We won by such a narrow margin, we would have been putting ourselves in the position of contesting our own election," he explained.

Moreau denies any irregularities in his favor. "The U.S. attorney checked us, too. And we were clean," he said. He has filed nearly 1,500 pages of documents - including the indictments - with the House Administration Committee in an effort to prove his contention that Tonry cheated his way into office.

The documents included the names of people such as Jean B. Saucier and Joseph Aiola of St. Bernard Parish. Saucier told The Washington Post someone forged her and her husband's names on voting certificates for the primary runoff.

"We didn't vote in that election because we were visiting our relatives in Vida, Tex., at that time," she said.

She said she had not intended to vote for Tonry or Moreau, but she said she believes the foregeries were done by Tonry backers.

Aiola, 67 and suffering from cancer, claims that one of Rowley's deputies barged into his voting booth and pulled the lever for Tonry over his objections. Aiola told his story to the grand jury. Tonry said he has heard it before and he calls it "incredible."

"He's an old man and he's batty," Tonry said.

The House panel investigating Tonry's election is not looking into allegations of illegal campaign financing. That matter is still before the grand jury.

In brief, Tonry associate Donald J. Zimmer is accused of lying to the grand jury about why he collected $32,000 in loans in the general election. Zimmer has contended that the money was collected for private investment purposes.

However, three of the men who each gave him $8,000 have sworn before the grand jury that the money was intended for Tonry's campaign. Federal law forbids individual contributions exceeding $1,000 to congressional candidates.

Tonry said that when he learned of the money collected by Zimmer - $8,000 of which came from Zimmer himself - he ordered his friend to return the contributions.

On another financial matter, between July 12 and 21, according to Federal Election Commission records, seven Tonry supporters - law partners, clients and relatives - each took out $5,000 loans to give to his campaign. In effect, each gave $4,000 over the individual limit.

Tonry acknowledged that those contributions may constitute a "technical" violation of the law when they were brought to his attention by a reporter.

But, he said, "There was no intent to do anything wrong. That's obvious. Why would I disclose it on my [FEC] records?

"Now, if it was a technical problem, I'll take whatever I'm supposed to get for making that technical mistake."