Maryland Gov. Harry Hughes today refused to join 20 other Democratic President Carter's reelection 1980.

Hughes, who received Carter's support last year in his gubernatorial victory in Maryland, was one of four Democratic governors who abstained from signing a resolution saying that the governors "enthusiastically endorse (Carter's) renomination and reelection to the presidency."

"i didn't come here to make a political decison," Hughes said after a meeting of the Democratic Governors' Association. "I'll make my decision in Maryland, where I think it should be made."

Hughes said it should not be inferred from his refusal to sign the resolution that he does not support the president. He said that he suggested to the Democratic governors this morning that they pass another resolution supporting Carter "in these very troubled times", but that the resolution stopped short of a political endorsement.

The governor said his decision had nothing to do with the rejection in a Baltimore federal court on Friday of a suit brought bu the state of Maryland against the federal energy department. In it, the state contended it is receiving less than its fair share of gasoline under the federal government's emergency allocation program.

Maryland may appeal the judge's ruling in that suit, Hughes said, but that decision will not be made until the governor meets with Maryland Attorney General Stephen Sachs later this week. (Sachs announced Saturday in Maryland that he would not appeal).

The other Democratic governors who refused to sign the resolution endorsing Carter were Joseph E. Brennan of Maine, Richard D. Lamm of Colorado and George Nigh of Oklahoma. In interviews, Brennan and Nigh echoed Hughes' reasons for not signing the resolution, saying they did not come to the conference to make a political decision.

The vote by the Democratic governors was followed here today by the opening of the National Governors' Conference. At an opening plenary session, Vice President Walter F. Mondale told the governors that "the panic (over gasoline supplies) is subsiding."

Mondale, substituting for Carter, who continued his meetings on energy at Camp David, said part of the reason for shorter lines at gas pumps is the in buying programs.

Virginia Gov. John N Dalton, however, disagreed today that the panic over gasoline supplies is lessening in his state.

"i don't think the crisis has passed," said Dalton, a Republican. "It is especially severe in Northern Virginia."

Dalton has authorized Virginia's energy chief George Jones to send 3.5 million gallons of gasoline to Northern Virginia to retailers who show hardship and an additional 1.5 million to gasoline station owners who agree to extend their hours of operation.

Dalton agreed with Hughes today that Carter is in trouble among voters across the country and in the Washington area.

"i'm not here to kick President Carter," Dalton said. But, he added that the president "would lose Virginia much worse today" than he lost it in the 1976 presidential election.

During the plenary meeting this afternoon, Dalton told the other governors that the federal government should ease clean air standards across the country to allow utility companies to convert oil-powered electrical plants to coal.

Later, Dalton said in an interview that six power plants operated by the Virginia Electric Power Co. could be converted to coal "in the next couple months" if the federal government would ease polution standards.

Dalton said such a move by the federal government would save scarce oil and is justified in "these times of crisis."

VEPCO has already announced plans to convert three of its oil burning plants to coal operation. Depending on the company's ability to meet federal air quality standards, the plants could be reopened late this year, Dalton said.