Alexandria Mayor Charles E. Beatley and City Council member Donald C. Casey may find their political careers harmed after yesterday's release of a special grand jury report, according to city and party officials.

The two closely aligned Democrats found no support for their criticism of Public Safety Director Charles T. Strobel in the report, which said Strobel did nothing wrong.

Beatley and Casey have led the assault on Strobel and called last week for his suspension. In doing so they have isolated themselves politically, gradually losing the support of the two other Democratic council members.

Democratic party officials fear the report gives opponents of the party ammunition for the May 7 City Council election, when both Beatley and Casey are on the ballot.

"Sure, I'm concerned with what this report says about two of our candidates," said Alexandria Democratic Party Chairman Joann Miller. "It's not favorable for the mayor or Don . . . and it doesn't look good for the Democratic Party.

In its report, the jury criticized the "callous, politically motivated activities of certain members of the Alexandria City Council in supporting the attempt to assassinate the character of . . . Strobel."

Republican council member Carlyle C. Ring said he hoped the report would change voters' minds about whom they want leading the city. He said the voter reaction to the report could lead to a "historic first for Alexandria -- a Republican majority" on the seven-member council.

"It's quite clear we have followed inept leadership in the mayor and Casey," Ring said. "They have led us down the road that has destroyed the reputation of the city."

Beatley, 68, a retired airline pilot running for his sixth term as mayor, long has been considered an unbeatable candidate. But the perceived weakening of his position over this controversy has prompted former Democratic vice mayor James P. Moran to say he is again considering running against Beatley, who is so far unopposed in the May election.

Moran, who is already in the race for council, said if he decides to challenge Beatley he will file as an independent by Tuesday.

Moran called Casey, a 42-year-old patent lawyer, "a frustrated criminal prosecutor" this week and said the mayor so identified himself with the city that he "got carried away. He thinks this is his kingdom. And he can't stand anything going wrong in it."

"There's got to be some political overtones with an election so soon," Beatley said yesterday. When asked how the report would effect Casey's chances in the election, the mayor responded, "I think a lot depends on what comes out later."

Beatley said a federal investigation has not been completed and that he is still concerned that the public safety department is mismanaged.

"If I had not raised any of these issues," Casey said yesterday, "I could have waltzed through this election."

Casey brought the allegations about Strobel's mishandling of a 1984 police drug investigation to the council's attention in a closed session Dec. 11. A nine-year council member, Casey is well known for his whistle-blowing role and acerbic tongue. He collected 9,500 votes in 1982 and placed third in a field of seven.

By raising the allegations in December, Casey said, he "made it a much more difficult election situation" for himself.

"As far as I'm concerned there was only one course of action because the issues being raised go right to the heart of the criminal justice system," Casey said. " . . . that's not the way you handle yourself if your main objective is to get reelected."