When Melvin A. Steinberg is sworn in as president of the Maryland Senate a week from today, he will face a myriad of problems, many routine, many complex, but none more difficult than the label a lot of people, friend and foe, will put on him.

Muldoon.

Here, where the name of Marvin Mandel still comes up almost daily, the term is a scary one for a politician because it connotes a connection with the days when Mandel was in the governor's chair and ruled the legislature with the backing of a cadre of loyalists who were known as "Marvin's Muldoons."

"I am not a muldoon," Steinberg has said several times since he successfully ousted James Clark Jr. as Senate president last month. Because he was friendly with Mandel and because he consulted with the former governor during his campaign for the presidency, Steinberg is the subject of whispers among people who say his rise could represent a return to the old days when Mandel would put his arm around legislators when he needed a vote and say quietly, "We'll work it out."

Steinberg acknowledges that he is conscious of the whispers. He has gone out of his way to appear statesmanlike since his triumph over Clark. He has not followed Maryland political tradition and punished his enemies. He is trying to make the Constitutional Public Law Committee, considered the Siberia of the Senate, respectable, assigning it new bills while fixing up the committee's cramped fourth-floor quarters.

Still, the whispers persist. The latest are about Steinberg's appointment of Anne Arundel County's assistant state's attorney, William Pitcher, as his administrative assistant, basically his chief of staff.

No one questions Pitcher's competence or his qualifications for the job. But one of the reasons--some people say the major reason--Pitcher was hired was a recommendation from Bruce Bereano.

Bereano is a lobbyist, the most oft-hired one in this town. He and Steinberg have been friends since Bereano first came to the Senate in 1973 to work for then-president William S. James. They became close friends between 1975 and 1979, when Bereano was administrative aide to Senate President Steny H. Hoyer. It was over lunch nearly a year ago that Bereano first suggested that Steinberg challenge Clark.

During Steinberg's campaign against Clark, Bereano was everywhere, talking to senators and prospective senators. As early as August he was confidently telling people, "Mickey's got it."

When Steinberg did get it, after a protracted and often bitter battle, a number of senators complained about Bereano's role. One of them, Sen. James C. Simpson (D-St. Mary's) a Clark supporter, made reference to Bereano's role during a speech in the Democratic Caucus attacking Steinberg.

Afterwards, both Steinberg and Bereano vehemently denied any potential for conflict of interest. "We're good friends and I respect Bruce," Steinberg said, "but that's as far as it goes."

Then came the hiring of Pitcher. Steinberg said he received about nine applications for the job and asked Bereano to interview several of the candidates. "Bruce knows what I need in that job because he's done it," Steinberg said. "I asked for his advice."

Bereano, after interviewing four of the candidates, advised Steinberg to hire Pitcher, who was once Bereano's intern when Bereano worked for Hoyer. Steinberg hired Pitcher. The question is not Pitcher's competence; the question is appearances.

"I know there are going to be people who are going to think something's going on or I have Mickey's inner ear but that's just not true," Bereano said. "I've done things in the past, like working to help get Mandel released from prison, that on the face of it may have looked funny to people. But I do what I believe in. I believed, outside my role as a lobbyist, that Mickey would be a good president. That's why I helped him. Period."

Steinberg: "Bruce is a close friend and I respect him. He is also a lobbyist. I recognize the potential for conflicts of interest but I don't think it will happen. I trust him not to try to take advantage and I know I won't let him."

Certainly, both men are aware of the whispers. Steinberg readily admits he is going to be guarded in his behavior this session. A sharp wit, he will probably spend a good deal of time biting his tongue to avoid making his trademark wisecracks from the rostrum. He will probably distance himself from the Mandel people and will be very careful about his involvement in bills in which Bereano has an interest.