Arthur A. (Bud) Marshall Jr., Prince George's County prosecutor for more than 20 years, said yesterday he is "very seriously considering" seeking a Circuit Court judgeship by challenging two sitting judges in next year's election.

Marshall's announcement, which came in letters this week to his staff and elected officials, may have a domino effect on the county's legal establishment. Circuit Court Judge Vincent Femia, who once served as Marshall's deputy, has already devised an elaborate plan that would allow him to replace Marshall as prosecutor and create a vacancy on the bench that could be filled by a sitting judge ousted by Marshall.

In Maryland, judges are appointed by the governor for 15-year terms, but must face the voters in the first general election after being named. Sitting judges are rarely challenged--it hasn't happened in Prince George's since the mid-1960s--and none has ever been defeated in the county.

Marshall, who was rejected for a seat on the Maryland Court of Special Appeals two years ago by a judicial selection panel that screens candidates for the governor, said he is making his intentions known because politicians already are being asked to support the two incumbent judges who must stand for election next fall.

"Rumors are flying throughout the Courthouse," Marshall wrote in an interoffice memo this week that at least partly confirmed them for his staff. "I will assure you that if I make the decision to seek a judgeship, each of you will be the very first to know. (Maybe my wife will come first.)"

Marshall urged officials to remain uncommitted "until such time as all the candidates are known and all the issues presented . . . . For many years, I have watched as voters have been precluded from this selection process. . . . I believe the community should have a voice in selecting those individuals who wish to sit as trial judges in the very community they would serve."

In an interview, Marshall decried what he said was a "lack of responsiveness to the public" by many judges who "go into their shells and won't answer questions or give reasons why they do what they do. The issue of electing judges is one of accountability."

However, many in the legal community disagree with that view and for years have called for adoption of "retention" elections at which voters would be given only the choice of confirming or rejecting sitting judges, and would be precluded from voting for other candidates.

Among the local proponents of retention elections are Ernest Loveless, chief judge of the 7th Circuit, which includes Prince George's, and Femia. Femia called the current system "a beauty contest" that requires judges to raise campaign warchests and attend kaffeeklatches that are irrelevent to the job.

Femia said the judges seeking election next September, Arthur (Monty) Ahalt and G.R. Hovey Johnson, are "super competent. I can see three good men vying for two positions and the public coming out on the short end by losing one."

Ahalt, former president of the County Bar Association, and Johnson, a former public defender, were appointed to vacancies, which is the conventional route that normally involves politicians and the bar.

"I've heard all those rumors" concerning Marshall and Femia, Judge Johnson said yesterday. "I'm not going to get involved. I'm running. Ahalt is running. We've decided to pool our efforts and run together as a team."

Should Marshall win a judgeship and resign as prosecutor, Femia said he would ask his fellow judges to appoint him interim prosecutor. He would then seek to have the vacancy created by his own career switch filled by the losing judge, by gubernatorial appointment.

Marshall, a native of Queens, N.Y., and a Korean war hero, was elected to his present post in 1962 on a reform ticket. He hasn't had any real opposition in a dozen years and says he can't even name his Republican opponent in the last election. "I never saw him," he said.

Femia was with Marshall in the prosecutor's office throughout the 1960s, serving as his chief deputy for three years before his appointment to the bench in 1972. He credits Marshall with bringing law and order to a county rife with "illicit gambling" and public corruption.

"He's the county benchmark for honesty and integrity," said Femia. Marshall, in turn, said Femia would "make an excellent state's attorney." He declined, however, to commit himself to Femia's plan.

Both men said they are motivated by career and retirement concerns. The salary is the same for both jobs, $58,500 a year.

Marshall, 52, said the judicial pension is better than that available to prosecutors.

Femia, a few years younger, insisted, "I have no burning desire to be the state's attorney, and I'm really not interested in playing musical chairs with Bud, but if he's gonna give up his chair. . . I'd like to see the level of professionalism maintained."

Femia has not been on the bench long enough to qualify for a judicial pension. To rectify that, Femia said several legislators have agreed to sponsor a bill in the upcoming General Assembly that would allow him to, in effect, buy four years' pension credit from his days in the state's attorney's office, when there was no retirement system available.

"Vince has always been a little bit of a frustrated prosecutor," said Marshall, who described Femia as a "friend for 20 years."

Marshall said he'd make a final decision on his own plans "within six weeks."