Prince George's County's all-Democratic delegation to the state Senate yesterday endorsed Maryland Gov. Harry Hughes for reelection to office, the first such public expression of support for a gubernatorial candidate by a group of state legislators this election year.

Sen. Thomas V. Mike Miller, leader of the county's Senate delegation, said the seven incumbent senators and a Democratic candidate for the vacant eighth seat met with Hughes last night and told him: "After much soul-searching we decided to support the Hughes-Curran ticket." Hughes' ticket mate as lieutenant governor candidate is state Sen. J. Joseph Curran Jr. of Baltimore.

Miller said the senators also told Hughes they were "dissatisfied with how the campaign has been run to date" in Prince George's, with little consultation between the statewide campaign staff and county politicians. Miller said Hughes told the group he "wanted to work with us and felt we had a good working relationship."

The decision by the Prince George's group, which Miller said was unanimous, followed an effort by Hughes' main Democratic opponent, State Sen. Harry J. McGuirk (D-Baltimore), to obtain neutrality if not an endorsement. Prince George's is a strong Democratic area and, along with Montgomery and Baltimore counties and Baltimore City, is considered a key to a successful campaign for a Democratic candidate.