County Councilman Melvin G. Mintz picked up another yea vote in his endorsement battle with Councilman Charles A. Dutch Ruppersberger III in the Baltimore County executive race.

Mr. Mintz, Mr. Ruppersberger and John C. Coolahan, former state senator and District Court judge, are the main candidates for the Democratic nomination for executive in the Sept. 13 primary. Kevin Pearl, a supporter of political extremist Lyndon LaRouche, also is running.

Mr. Mintz received the backing this week of Teamsters Joint Council 62, which represents 20,000 members, 6,000 of whom are in Baltimore County.

As he has said numerous times in his campaign regarding endorsements, Mr. Mintz noted that he received the support "without backroom deals and unfulfilled promises."

Mr. Ruppersberger has maintained that he has promised nothing more than that to the groups that have endorsed him. Mr. Mintz had sought the same endorsements.

Chuck Stansberg, Teamsters' council president, said his union endorsed Mr. Mintz because "we don't need someone with slick political answers. We appreciate Mel for his straightforwardness."

Mr. Mintz said he couldn't prove that Mr. Ruppersberger made back room promises. Mr. Mintz said that since he had such a good record of supporting county public employee unions, he should have earned their endorsements. Because of that, he said, Mr. Ruppersberger must have offered the unions something.

"Dutch has offered these unions and other organizations something for their endorsement," said Bob Barrett, Mr. Ruppersberger's campaign coordinator. "He has offered them his experience, his extensive background and his proven ability to manage and to lead."