Anne Arundel County Executive Robert A. Pascal, the only major Republican figure in Maryland known to be considering running for governor, says he will not enter the 1982 election if William Donald Schaefer, the Democratic mayor of Baltimore, wants to run.

Pascal, who has spent the last three months taking soundings throughout the state on a possible 1982 challenge to Democratic Gov. Harry Hughes, says he would step aside for Schaefer, despite the mayor's Democratic Party registration, for reasons of friendship and practical politics.

"Not only is he a friend," the stocky, gravel-voiced Pascal said yesterday in an interview at The Washington Post, "but I don't think anyone can beat him."

Pascal said he has spoken several times to Schaefer, the bachelor mayor renowned for his Baltimore boosterism, but does not know yet what the three-term incumbent intends to do in the 1982 race. A Schaefer primary challenge is considered a possibility because of Schaefer's increasingly public dislike of Hughes, who he says has ignored the needs of Baltimore.

Despite the speculation about a Schaefer candidacy, most recently sparked by a "nonpolitical" testimonial given in his honor that raised $250,000 Pascal and his aides maintain that the mayor is unlikely to run because he is so tied to his city. Besides, says Pascal, "Donald knows he'll get a fair shake if I'm elected."

So, notwithstanding the pledge to withdraw from the race in favor of Schaefer, Pascal has been crisscrossing the state speaking to groups and talking to contributors to assess his chances against Hughes, who has not yet offically said he will seek reelection.

But doing so, Pascal has become the leading Republican contender for the governor's mansion 15 months before the 1982 primary. The party's other well-known figures, such as Rep. Marjorie Holt and Prince George's County Executive Lawrence J. Hogan, are focusing instead on the 1982 race for the U.S. Senate seat now held by Democrat Paul Sarbanes.

Pascal has made similar moves for governor before -- in 1978 he was poised to announce his candidacy but backed off, leaving the party scrambling for a candidate. But this time Republican officials say he is sounding like a committed man. "He's no longer saying, 'If I run,' He's now only saying, 'When I run,'" said one Pascal associate.

In part, this is because the executive is serving his second term and under county law cannot run again. And in part, Pascal, like many Republicans, believes that there is a growing sense of disenchantment with Hughes among the electorate and party officials.

While admitting this is a bit of wishful thinking, the Republicans have been poring over a recent poll done by Arthur J. Finkelstein Associates of New York for the state Republican Party. According to the survey of 505 likely voters, Hughes would beat Pascal by 43 percent to just over 22 percent if the election were held today. But nearly 35 percent of the voters were uncertain about whom to vote for and 24 percent of those surveyed rated Hughes unfavorably. Another 47 percent gave him favorable marks and nearly 27 percent had no opinion.