Maryland Attorney General Stephen H. Sachs began paving his campaign trail in Prince George's County yesterday, wooing black leaders, union officials and some politicians but failing to add County Executive Parris Glendening to the list of announced supporters for his gubernatorial campaign.

Throughout the day, Sachs shadow-boxed with the unannounced candidacy of Baltimore Mayor William Donald Schaefer, a popular figure who is expected to be his toughest opponent. House Speaker Benjamin L. Cardin is also in the race.

"There's no mystery about the fact that I think it's too early [to endorse]," Glendening said at a New Carrollton senior citizen luncheon at which he introduced Sachs. " . . . Any one of the three would be a very good governor."

More than 50 black elected officials and community activists who attended a campaign breakfast in Hillcrest Heights earlier in the day welcomed Sachs warmly. Several who also had attended a private meeting with Schaefer last July in Upper Marlboro said after yesterday's meeting that they felt more comfortable with Sachs' responses to questions concerning education and minority development issues.

"Schaefer got asked all the same questions, but his response was a rebuking, a dismissal, which fascinated everybody and intensified the probing," said Wayne Curry, a Landover lawyer who described the Schaefer gathering organized by Glendening as more of a "political business meeting."

"We have a pretty powerful local agenda," added Alvin Thornton, a supporter of Sachs. "And [Sachs is] going to have to sit on top of that."

County black officials are touting lawyer Alexander Williams, who is black, as a likely challenger to State's Attorney Arthur A. Marshall next year, but Sachs said he has not decided who to support in that race.

Eight Prince George's County delegates to the General Assembly also held a press conference in Greenbelt yesterday to formalize their support for Sachs, declaring themselves independent of the county's prevailing Democratic organization.

"This is a county where most elected officials wait around to be told who to support by one or two individuals," said Del. Frank Pesci (D-New Carrollton).

"What does bind us is a sense of political independence," Sachs said to his supporters at the meeting, who included Dels. Pauline Menes, Joan Pitkin, William Bevan, Pesci, Albert Wynn and David Bird. "Public office is not simply doing what you're told by someone or some force who styles itself as your leader."