Maryland Attorney General Stephen H. Sachs, after completing an audit into voting patterns in Dorchester County, has found that the Eastern Shore county's at-large system of electing county commissioners violates the federal Voting Rights Act.

The finding by Sachs, who began an inquiry into voting practices in several Maryland counties last summer, corroborates an investigation by the U.S. Justice Department, which filed suit two weeks ago in federal court charging Dorchester County and its county seat, Cambridge, with Voting Rights Act violations.

"The heart of the matter is a history of racial polarization" in the Eastern Shore county, where blacks constitute about 30 percent of registered voters, said Sachs last night after informing the county commissioners of his findings. "We believe the conclusion the court would come to is that there has been a dilution of the ability of the black community to elect candidates of their own choosing."

Despite a large black population concentrated in Cambridge, Dorchester County has never elected a black to its five-member board of commissioners. The county's system of at-large elections was mandated by the state constitution in 1851.

Sachs met with Gov. Harry Hughes yesterday and recommended the state intervene in the federal lawsuit by presenting to the U.S. court its own findings of discriminatory practices and by submitting a redistricting plan that would satisfy the 1982 amendments to the 1965 Voting Rights Act that prohibit voting regulations that exclude minorities.

The Justice Department's Maryland suits -- it also filed suit against Cambridge, where city commissioners are elected at large -- are the first federal actions under the 1982 amendments brought outside the deep south. Federal courts in the south have in the last year ordered a number of local governments to abandon at-large voting systems as inherently discriminatory.

The critical test in such cases, Sachs said yesterday, is whether black voting strength is unfairly diluted by at-large elections. Among factors that are considered are the extent to which there has been a history of poor race relations and whether there is a pattern of whites voting against black candidates.

Sachs said his audit found that blacks running for county-wide office in Dorchester had consistently won more than 50 percent of the vote in black communities but as little as two percent in white areas.

The audit did not deal with the separate question of Cambridge city elections.

Sachs said he expects the state to offer Dorchester County technical assistance in re-drawing its district lines. "We have a lot of reason to believe that lines can be drawn which are fair," he said.

"The county seemed receptive," said Sachs after his meeting with Dorchester commissioners last night. "They expressed a desire to cooperate with the state."

Leonard Dayton, the president of the county commissioners, could not be reached for comment.