A poll done for Maryland Republican gubernatorial candidate Robert A. Pascal shows that he must overcome a serious name recognition problem, especially in the important Washington area, if he is to defeat incumbent Democratic Gov. Harry Hughes.

In a poll of 600 registered voters by Lance Torrance, a Republican pollster from Texas, during the last two weeks of April, Pascal trailed Hughes in a head-to-head vote 55 percent to 25 percent, with 20 percent of the voters undecided. Pascal, the Anne Arundel County executive, attributed that deficit yesterday to the fact that few voters recognize his name. The poll has a 3 to 5 percent margin for error in either direction.

Only 29 percent of those polled knew who Pascal was compared with the 97 percent who knew Hughes. In the Washington area, Pascal's name recognition was only slightly better than 10 percent.

More encouraging for Pascal was the question put to voters on whether they would vote for Hughes against an unnamed opponent. Thirty-one percent said yes, 26 percent said no, and 43 percent were undecided.

"I think the more important question at this point is on whether people would reelect Harry Hughes," Pascal said. "I've known since I first got in this race that name recognition was going to be the first thing I had to overcome. But I think if you've got an incumbent who is only getting a 31 percent favorable rating, that means he's ripe for plucking."

Pascal has been advised by Paul Newman, his $900-a-day consultant, to aim to beat Hughes in the last 90 days before the Nov. 2 election. "I don't have the resources to run a five-month campaign," said Pascal, who has raised about $200,000, about half of what Hughes has raised for the campaign.

But with the poll confirming his limited name recognition, Pascal is planning to begin TV ads early next month in Washington and Baltimore. He will also name a running mate then, probably someone from Montgomery County to boost his campaign here.

"This election is going to be decided in Prince George's and Montgomery counties," Pascal said. "I'm going to run very strong in the city of Baltimore, get up to and maybe more than 50 percent of the vote."

All of those responding to the 42-question telephone poll had voted in the 1980 presidential election, according to Pascal campaign officials. Thirty-six percent of them classified themselves as "mostly Democratic" voters and 14 percent said they voted for Democrats slightly more than for Republicans. Thirteen percent said they were "mostly Republican" voters and 15 percent said they voted for Republicans slightly more often than Democrats. Twenty-two percent classified themselves as independents.

The Hughes campaign did a poll this week as a followup to a three-week television advertising campaign. Campaign manager Joseph M. Coale III said the poll of 450 voters showed Hughes defeating Pascal 54 to 22 percent. In March, Coale said, a similar poll showed Hughes leading 46 to 28 percent.

"We did our poll right in the middle of his Hughes' TV ads ," Pascal said. "No question that gave him a wider margin than he would have gotten otherwise. I still think when October comes, he is going to hear my footsteps."

"We think this poll shows that Harry Hughes is the most vulnerable incumbent Democratic governor in the country," said Fred Roberts, who joined the Pascal campaign from the Republican National Committee early this month. "We are greatly encouraged by it."

Democrat Coale disagreed with Roberts' analysis. "If they are encouraged by those numbers they must be coming from Disneyland," he said. "Their figures are not terribly different from ours, which at least gives the poll credibility. But the 50 to 55 percent figure reflects solid Democrats. In a year like this that isn't going to go down." Although Pascal has not run as a Reagan Republican he is expected to ask the GOP national committee for financial help this summer, using the "vulnerability" shown in the poll as a justification.