Prosecutors in the drug and perjury trial of D.C. Mayor Marion Barry began asking potential jurors for the first time yesterday whether their views of the case would be altered if the mayor abandoned his reelection plans.

Close associates of the mayor, speaking on condition of anonymity, had been suggesting since late last week that the mayor was on the verge of declaring he would not be a candidate in November. Barry ended the speculation last evening, saying he would not seek a fourth term this fall.

Yesterday's inquiries in the courtroom, by Assistant U.S. Attorneys Judith E. Retchin and Richard W. Roberts, were the prosecutors' first response to the earlier reports that Barry would make that announcement. Although members of the jury pool have been instructed to avoid news accounts "about any aspect of the case," Retchin and Roberts asked most of those who took the witness stand yesterday whether they were aware of the mayor's political plans.

"Have you heard any of the more recent reports concerning the announcement by Mr. Barry of his plans for reelection?" Roberts asked Roger J. Nordean, an Internal Revenue Service employee who took the stand as juror number 190.

"No," Nordean replied.

"If you heard outside the case that the mayor planned not to run for reelection," Roberts asked, "Would you have trouble disregarding that information?"

"No," Nordean replied.

None of the jurors examined yesterday answered otherwise.

But when defense lawyer R. Kenneth Mundy took up the subject, he got what appeared to be a surprising response.

"If you learned . . . that Mr. Barry was not going to seek reelection, would that in any way give you the impression that he was doing so because he was guilty?" Mundy asked.

"Yes {it} would," replied Johnnie Jackson, juror number 124.

"Why is that, sir?" Mundy asked.

"Because if he quit before the trial, that's saying that," Jackson replied.

Barry, who had been reviewing documents at the defense table, removed his reading glasses and stared intently at the witness. Other jurors, asked the same questions, said they would have no such reaction to the announcement of Barry's political plans.

Of 15 jurors examined yesterday, seven were excused by U.S. District Judge Thomas Penfield Jackson. Four were excused at the judge's initiative, two for medical reasons, one because of urgent personal business, and one because she did not think she could be fair.

When it came time for the lawyers to argue for further exclusions, however, Judge Jackson for the first time in the trial held the argument at the bench. Deputy U.S. marshals assigned to courtroom security declined to transmit to the judge written requests by The Washington Post and WTTG-TV (Channel 50) that the arguments be held in open court. When Beverley Lumpkin of ABC News urged the marshals to transmit the notes, the marshals made her leave the courtroom.

In an interview after the hearing, Jackson said he had held arguments at the bench so that prospective jurors would not know which side sought to exclude them. In previous articles this week, The Post has reported those arguments, and Jackson said he feared such reports might taint the jury.

All told, 127 of the 250 randomly selected potential jurors have now been interviewed. Jackson has qualified 77 of them to hear evidence in the case.

Judge Jackson said yesterday that the initial round of examinations will stop at noon tomorrow. On Monday morning, he said, the lawyers will make their final peremptory cuts -- those for which neither side need give a reason for striking. Twelve jurors and six alternates will be seated.

"The trial proper should be able to start promptly on Tuesday morning," Jackson said.

In addition to questions about Barry's political plans, Retchin and Roberts for the first time began probing prospective jurors for concerns about the mayor's sentence, if convicted. As part of their standard instructions, jurors will be told that they must not consider the possible sentence in deciding guilt or innocence. The new questions by Retchin and Roberts followed extensive discussion in news reports of the possibility that the mayor could face jail if convicted.

"Would you be able to take out of your mind any concern about what Mr. Barry's sentence might be in the event of a conviction?" Retchin asked a young woman, whose name could not be heard from the gallery.

The woman, like all the jurors questioned, said she could do that.