Maryland Republicans, still basking in the glow of 1984 election victories, moved today to maintain last year's momentum by formally urging Howard County Executive J. Hugh Nichols, a Democrat, to switch political parties so that he can run as the Republican candidate for governor in 1986.

Nichols, 53, has been Howard County's top elected official since 1978. Reached at his home after today's action, he said that he was "flattered" and is considering making the shift.

"It's something that I've thought about, off and on, for a long time," he said.

More than 200 persons attending a convention of state Republican Party officials here this weekend signed the pro-Nichols petitions being circulated by Howard County State Central Committee members.

"Knowing Hugh Nichols, because he has been a lifelong Democrat, this will be a difficult step for him to take," said GOP state party chairman Allan C. Levey.

The sentiment to draft Nichols was not universal among Republicans here. In part because of this, a resolution that the 183 elected convention delegates approved on a voice vote merely invited Nichols to become a Republican and omitted any reference to a gubernatorial race.

"I caution us to be very careful," said Jim Wright of Anne Arundel County. "A lot of us really don't know where the man stands. He could be the best thing since motherhood and apple pie, but we do not know where he really stands on the issues."

But Joan Athen, chairman of the Howard County Republican Party and the moving force behind the draft-Nichols movement there, said Nichols' philosophy fits the Republican mold.

"What [Nichols] wants to see is a number of supporters from the grass-roots level," she said.

John Burcham, chairman of the Prince George's Republican State Central Committee, said that he sees support for a possible Nichols candidacy in other areas of the state, as well.

"Part of the message coming out of this convention this weekend is that the Republican Party is still on a high," Burcham said. "We're still in the position of being able to attract very capable people."

Speakers Friday and today stressed the importance of building Republican ranks in Maryland by encouraging Democrats to switch.

Republican National Committee Chairman Frank J. Fahrenkopf cited such ex-Democrats as President Reagan and former U.N. ambassador Jeane Kirkpatrick as examples. He made special reference to William Lucas, the black county executive of Wayne County, Mich., who switched his party affiliation to Republican last week.

Lucas has also been promoted by his state's party as a possible gubernatorial candidate.

"Wouldn't it be prophetic that the first black governor elected in this country is a Republican?" Fahrenkopf said during a luncheon speech.

If Nichols decides not to become a Republican, party leaders said that Anne Arundel state Del. Robert Neall or Montgomery County Del. Constance A. Morella are the two next likely candidates for a Republican nomination.

Morella was not at the convention, but Neall, 36, who was elected to a party office here today, said he is considering such an option.

"One advantage we could have is to have a candidate who could be a thoughtful alternative to the shrill debate on the other side," Neall said, in an apparent reference to the battle that may be shaping up for the Democratic gubernatorial nomination among Attorney General Stephen H. Sachs, Baltimore Mayor William D. Schaefer, Speaker of the House Benjamin L. Cardin and, until recently, Nichols himself.