Allan C. Levey, chairman of Maryland's Republican Party, was talking to his candidate for governor, Robert A. Pascal, during one of the many lulls in the party convention this weekend. Throughout the two-day affair, Pascal repeatedly had been asked one question by party workers and reporters: "When are you going to pick a running mate?"

Levey asked the question differently: "Have you narrowed your list?"

"Oh yeah, I have," Pascal answered.

"How many left?" asked Levey.

"Thirteen."

Levey laughed; Pascal didn't. Although he does not have a list of 13 names, he might as well because, according to party sources, Pascal is no closer to choosing a running mate than he was when he announced his candidacy three months ago.

"Why does everyone keep asking me that question?" Pascal said. "Why don't they ask the other guy about who he's going to ask?"

The other guy is Gov. Harry Hughes. The only thing certain about the Hughes candidacy is that the current lieutenant governor, Samuel W. Bogley, will not be on the ticket. Neither will Speaker of the House Benjamin L. Cardin or Baltimore County Executive Donald B. Hutchinson, Hughes' top two choices for the job. State Sen. Harry J. McGuirk (D-Baltimore), who has announced his opposition to Hughes, also is without a No. 2 candidate.

So why all the pressure on Pascal?

"Because everyone in the party is antsy," said Sen. Edward P. Thomas (R-Frederick). "People think this is really a year of opportunity for the party in this state and they want to get cranked up and get going. But you can't march down Main street with a brass band in May without being burnt out by July."

That is the theory of Pascal's mentor and chief advisor, Herman Intemann, the former state transportation secretary. Throughout the convention, Intemann told people, "You can't be out in full force this early. You don't want to wear out your troops before you even know who your colonels and majors are going to be."

But while Pascal has moved ahead slowly, possible lieutenant governor candidates, unable to wait for a decision, have headed in different directions. Pascal would like his running mate to come from Montgomery County because he knows his name recognition is almost nil in the Washington area.

The two Montgomery politicians mentioned most often have been Dels. Constance A. Morella and Luiz Simmons. Both let it be known early in the year that if Pascal asked, they would be interested. Pascal has never sent them a clear signal.

The Pascal approach, or nonapproach, can be described by an incident that took place towards the end of the General Assembly session. Simmons was leaving Cardin's office when he bumped into Pascal in the hall. Pascal took Simmons aside.

"What are you going to do, have you decided yet?" Pascal asked.

"Well Bob, as of right now, I'm running for County Executive assuming I can raise the money." (Simmons said yesterday he has received commitments for $75,000 in the last week and will announce his candidacy for the Montgomery County executive's race May 18).

"Okay, pal," Pascal said.

Simmons said later, "We had at least four conversations like that where he asked me what I was doing. But he never said to me, 'Would you be interested in running with me?' I had to go ahead and plan my campaign. I couldn't wait."

Neither could Morella, who will announce her reelection plans May 23. She was the candidate recommended to Pascal by the Montgomery Central Committee.

Now, party sources speculate, Pascal probably will have to turn to someone who is not an office holder. The name of J. Willard Marriott Jr., son of the hotel baron and a Montgomery resident, has been tossed around.

Another name being mentioned is that of former U.S. Rep. Newton I. Steers. State Sen. Howard A. Denis, who told Pascal early on that he was not interested in the slot himself, called Pascal several weeks ago to recommend Steers after learning that Steers, who has been out of office since losing to Rep. Michael Barnes in 1978, would be interested.

Levey, who lives in Montgomery, also would be interested, but his relationship with Pascal, although friendly, is not warm. In fact, Pascal and Levey had what witnesses said was a fairly heated debate over breakfast several weeks ago in Annapolis because of Pascal's failure to appoint county chairmen and get his local campaigns operating.

"It wasn't heated," Levey said. "We were just having a discussion. I think Bob may be waiting for Hughes to pick his running mate before he picks his. He doesn't want to rush into this and make a mistake."

Pascal said he will have his county chairmen in place this week. This morning, in Baltimore, he and several other "money people," will listen while Paul Newman, a $900-a-day consultant, tells them what he thinks should be done to get his fundraising moving. He now has a paid campaign manager, Fred Roberts, a former employe of the Republican National Committee.

But, he does not have a running mate and few in the party have a clue who he will choose or when he will make his choice. When Pascal was asked Saturday when he would announce the second half of his ticket, he smiled and gave his best politician's nonanswer:

"Soon."