The two state senators were taking advantage of a tedious Senate session to duck into the hallway for a cigarette and some frank talk about the tax reform legislation before them. "Didn't we kill this bill last year?" one asked the other. "What's happening here?"

"Simple," his colleague replied. "Last year Ben Cardin didn't want this bill. This year he does."

The senator's remark was laced with a mixture of respect and irritation as he evoked the name of the 34-year-old Baltimore delegate. Respect, because Maryland legislators almost always accord respect to a colleague who has the skill and clout to get his way.

Then irritation, because the senator who spoke was not from Baltimore. Cardin, a precociously successful delegate who was only 29 when he moved into the chairmanship of the powerful House Ways and Means Committee, consistently used his legislative skills on behalf of bills that funnel millions of state dollars into Baltimore City.

There was one more thing about that brief corridor conversation: its tone was vaguely familiar. It was the same tone that legislators once used when talking about Marvin Mandel. Their resentment over legislation damaging to their own interests was often outweighed by their admiration for Mandel's deft mastery of the legislative process.

The comparison is admittedly stretched, although not overly so. For the first time in nine years, suspended Gov. Marvin Mandel is absent from the statehouse, awaiting word on the appeal of his political corruption conviction.

His absence, coupled with the more low-key executive style of Acting Gov. Blair Lee, has given legislative leaders like Benjamin L. Cardin - who represents Mandel's old district, the tightly-knit, heavily Jewish area in northwest Baltimore - to fill the power vacuum Mandel left behind.

Along with other leaders, like Senate President Steny H. Hoyer, Cardin has taken ample advantage of the opportunity. This year he has pursued his legislative goals so successfully - without making a single enemy - that his name is constantly tossed about in the election-year speculation about who will fill the second spot on Lee's gubernatorial ticket.

Cardin discounts the talk. He freely admits, "I would like to be Speaker of the House next year," but adds that "if John (House Speaker John Hanson Briscoe, a close friend of Cardin's) comes back next year, I'll be the first to renominate him."

This sort of modesty and self-effacement have become something of a joke among legislators: it led House Majority Leader John S. Arnick to do an impromptu spoof on Cardin's understated style at the annual Legislative Follies show last month.

Nonetheless, Cardin's colleagues seem to take statements like this at face value. Janet Hoffman, a Baltimore City lobbyist who combines a canny mind with an almost motherly approach to legislators, explained that "he's able, but his ability is not accompanied by conceit.

"He has a sense of his own worth and the value of his judgments but he is not overly impressed with himself. And he is very even-handed in how he deals with people."

Most people here credit Cardin's even-handedness and his straightforward style for his crowning success of this legislative session: the seven-bill package of property tax relief legislation that is on Lee's desk to be signed into law.

In assembling the package, which was the product of long hours of negotiations between Lee and Senate President Steny H. Hoyer and Briscoe and Cardin and Sen. Roy Staten, Cardin put almost all of his formidable mastery of tax laws into play.

He also put aside his own chief priority - reform of the state's income-tax laws - in order to cope with the inexorably rising property taxes that had both legislators and homeowners screaming for relief measures.

The House of Delegates was inching its way through a long series of committee reports last week when Del. F. Vernon Boozer, a Baltimore County Republican, stood to make a motion. It was a motion that Cardin knew was coming, but one he still did not want to hear.

One of the bills Boozer had introduced, a measure requiring state assessors to reassess homes every three years instead of every year, had been killed by Cardin's committee.

Boozer now was seeking to get the House's consent to override the committee and revive the bill. This left Cardin in something of a dilemma. While not necessarily opposed to a triennial assessment system, Cardin agreed early in the session that this would not be part of the property tax relief package.

Boozer's was not the only property-tax relief measure that Cardin and his committee had agreed to kill, in order to win support for the package from all the warring factions in the legislature. If the Boozer bill was revived, Cardin said later, "the floodgates could have opened."

Other delegates might have tried to get their measures revived, and this flood of extraneious legislation could have torn the property-tax package apart.

As the motion was made, Cardin quickly got to his feet. With the cord of his desk microphone curled around his hand, he started to speak rapidly.

"You can take away any one of the seven bills in the package and pick it apart. But as a package it makes sense . . . This was not put in the package."

Then Briscoe called for the vote the motion. Cardin half-turned, squinting up at the voting board through his wire-rimmed glasses. Boozer's motion had failed by a vote of 53 to 65.

Then, in an action rarely seen on the floor of the House, Boozer stepped across the aisle that divided him from Cardin and shook Cardin's hand.

"Ben could have let that bill languish in committee without voting on it, giving Boozer no chance to even make the motion," one legislator explained later. "But he didn't. He was fair; he let Boozer have his shot."

"Ben just has a way of presenting issues and working out fair resolutions when you have opposing views to deal with," explained House Speaker John Hanson Briscoe, who was chairman of the Ways and Means Committee when Cardin was its 27-year-old vice-chairman.

"He does that partially through personality; he's sensitive to strong points of view and he has a way of making people feel that he's working things out for them, or at least trying," he said.

Laurence Levitan, who plays tennis with Cardin on Tuesday mornings and spends most of the rest of the day trying to fight Cardin-endorsed proposals and get more money for his Montgomery County district, also speaks of Cardin with respect and trust.

Levitan points out how Cardin manages to be effective in the legislature, and still bask in the affection and trust that are highly unusual in this jealous and egocentric world.

"He's got the ability to deal with every element in the House, but he couldn't be effective without Paul Weisengoff and without Janet Hoffman." Hoffman coached Cardin on tax legislation in his early years in the legislature; now she teams up with him to push it through.

Weisengoff, the head of the Baltimore City delegation, uses not-so-gentle legislative muscle to back up Cardin's legislative reasoning. When Cardin needs votes on an issue, Weisengoff, who sits on the Ways and Means Committee and is also one of the more skilled vote-traders in the legislature, gets them for him.

"I need a whip, and Paul's a whip in the best sense of the word," Cardin agreed.

"Just being in his house as a child was different from being in my house," said Myrna Cardin, Cardin's wife of 11 years and his one-time elementary school classmate. "My father managed a shoe store and life was very predictable. All you had to do was step into his house to know things were happening."

Things were happening at the Cardin home in northwest Baltimore. Governors and powerful state legislators would come and go. Cardin's father, Meyer Cardin, worked his way up through politics, serving briefly as a state legislator and eventually becoming a judge.

His uncle Maurice is presently a member of the state workmen's compensation commission; his cousin Jerry is active in Baltimore County politics and land deals; and another cousin, Morton Rosen, is his law partner.

The accolades accorded Cardin in the legislature have not always been accorded to other members of his family, however. For instance, his cousin Jerry Cardin has made quite a few enemies in his dealings over the past few years.

But in northwest Baltimore, the Cardin name means something - perhaps, on a smaller scale, one can like it to what the Kennedy name means in Boston.

The fact that he got his chance to succeed in politics through his family's influence and the shifting alliances of northwest Baltimore politics does not bother him. "The question is how you use your good fortune," he said.

"I'm not flamboyant. That doesn't bother me," he said. He also does not work at promoting a public image of himself like many of his colleagues. His importance in this session has led many reporters to camp outside his office.

Then there are plenty of other people around to do his promoting for him. His cousin and law partner, H. Morton Rosen, called a reporter last week to announce that Cardin had been to the White House for a discussion seminar on President Carter's urban policy program.

"The guy has a terrific future," Rosen bubbled. "We're grooming him to be a governor."

Cardin calls such speculation by his friends "Naive. So many things can happen in four years' time. I'm not ruling anything out, but I'm just not thinking about it."

Del. Raymond E. Beck, a Republican on Cardin's committee, accepts this kind statement without much question. "He's the kind of guy following a political star and he doesn't really know where it will come to rest."