The dog days of summer have done nothing to slow the pace of pre-election year politics in Maryland, as was evidenced by a minor fiasco that took place last week in the offices of Prince George's County Executive Parris Glendening.

Glendening, long a pal of unannounced gubernatorial candidate William Donald Schaefer, the mayor of Baltimore, said that as a political courtesy, he offered to organize a "candid, private discussion" for Schaefer with a handful of Prince George's black officials.

But the meeting backfired, according to the six people who participated in the session with the county executive and the mayor in Upper Marlboro. Among other things, participants said, Schaefer praised Ronald Reagan, said he himself was in favor of capital punishment and, one participant said, showed "absolute condescension" to those in attendance.

"I wasn't impressed," declared another who was there, County Council member Hilda Pemberton. "The mayor didn't seem to be interested in having Prince George's County support him at all."

"I would say he wasn't very sensitive to the plight of the constituency we represent," said Bennie Thayer, president of the state Rainbow Coalition. "And that's putting it as nice as I can."

Thayer has said in the past that he has all but eliminated Schaefer from his thinking as an acceptable candidate and is leaning toward endorsing Maryland Attorney General Stephen H. Sachs for governor in the 1986 election.

But others at the meeting who have not been courted as intensely by candidates Sachs, Schaefer and Speaker of the House Benjamin L. Cardin said they also were unimpressed with Schaefer, who was characterized as "defensive" and "arrogant" by several of those who attended the meeting.

"When I walked out, I didn't know one person who I walked out with who felt that he came across convincingly," said James Fletcher, the new mayor of Glenarden. Fletcher said he also was disappointed that Schaefer has not yet publicly stated his intention to seek the governor's office.

In private discussions, Schaefer has made clear he intends to run for governor, although his aides insist he should not be perceived or treated as a formal candidate.

Participants said Schaefer spent a lot of time at the Prince George's meeting talking about his accomplishments in Baltimore and little time saying what he would do for the state if he were elected governor.

"I said 'If you were governor, what would you do for education?' " Pemberton recalled. "He said, 'What have you done? You're an elected official.' But I thought, 'I'm not running for governor.' "

Schaefer aide Jim Smith, a Baltimore businessman who is organizing the mayor's fall fund-raiser, characterized the Prince George's meeting as a "give-and-take session" with what he called "the activist community."

"The black community in Prince George's has not gotten to know the mayor well," said Smith, who managed Schaefer's 1983 mayoral campaign. "But the black community in Baltimore . . . has given him a stupendous endorsement."

Schaefer was elected to his fourth term as mayor of Baltimore in 1983 with an overwhelming mandate that included the backing of the majority of the city's large black community. He had earlier turned back a challenge from a black opponent in the primaries.

Glendening, who has not publicly endorsed any candidate, said he would arrange similar meetings for those who requested them. But he said that the "chemistry was not good" at the recent meeting, adding that Schaefer was unwilling to make any promises about what his administration would do for black people.

"The bottom line is it really wasn't a very good meeting," he said. "I could feel that the vibes just were not good at all."

Glendening, who faces a reelection race next year, also could have been indirectly damaged by the failed meeting, in part because some of those at the meeting resented his presence as a go-between. "He put the whole deal together and it blew up in his face," said one attendee.

"I think [Schaefer] severely damaged any early opportunity he had to build credibility in the black community," said lawyer Wayne Curry, a Rainbow Coalition member who was at the meeting. "We were incredulous and, frankly, suspicious of whether he really wants to be governor."