For more than an hour, Maryland House Speaker Benjamin L. Cardin had been talking to 80 people in a small auditorium in Prince George's County. The topics had ranged from the relationship of the General Assembly and the governor, to Maryland's savings and loan crisis, to housing conditions in the county.

One subject had not come up, though it dominates Cardin's thoughts these days: the 1986 campaign for governor. Not until 10 minutes from the end of the program did a questioner bring it up.

"This is not politics," muttered a Baltimore political writer who had come to see Cardin toot his gubernatorial horn.

Yet it was politics, Cardin style and typically understated, the kind of talk that the 41-year-old Baltimore legislator hopes will propel him to the State House in January 1987. He plans to become Maryland's 58th governor no matter what the polls and the pundits and the insiders think.

Cardin has spent this summer doggedly trying to establish his credibility as a candidate, overshadowed by his likely Democratic opponents, state Attorney General Stephen H. Sachs and Baltimore Mayor William Donald Schaefer, and largely written off by some of the media. (A recent article in the Baltimore Sun on the governor's race never even mentioned his name.)

Supporters such as Del. Charles Ryan (D-Prince George's), who know Cardin as a masterly legislative tactician and student of state government, are frustrated that the speaker's talents remain little known.

"Everyone in Annapolis realizes what an outstanding individual he is, but to the average guy in the street, Ben Cardin is just a guy from Baltimore," said Ryan, the chairman of the Prince George's House delegation.

Unfortunately for the speaker, another person named Cardin, his first cousin Jerome, is getting as much publicity as he is, if not more, and it is not favorable. As a minority stockholder in the troubled Old Court Savings and Loan Association, Jerome Cardin has been linked to alleged improprieties at the institution where Maryland's savings and loan crisis began.

The effect of that is unclear, but Ben Cardin will begin polling soon to determine the impact.

In an era when politics has gone high-tech, Cardin's campaign is almost quaint. To be sure, he has hired his share of consultants to help him with polling, direct mail and fund-raising. But when he is out on the road, it seems more like a traveling civics lesson than a political rally.

On the stump, Cardin talks knowledgeably about the need to reorganize Maryland higher education, the importance of dredging Baltimore's harbor, and the necessity of trimming health care costs. But he rarely comes out and says, "I'm running for governor and I need your help."

His style is worlds apart from his opponents. With Schaefer, you get star quality, the walking embodiment of Harborplace and Baltimore's rebirth. With Sachs, you get a philosophical descendant of FDR, a prosecutor with a liberal heart and stem-winding oratory. With Cardin, you get pure substance. Sometimes, you get substance till it hurts.

"I don't want politics as usual," said Cardin. "I want people to vote for the best person to be governor. I think if I try to go on the political side, or the flashy side, I'm going to come out second best. So I'm going to stick to substance."

In some circles, substance equals dull, which Cardin has been accused of being by many, including colleagues in the legislature. If Cardin had a dollar for every piece of advice he has gotten on how to refashion his image, he could buy the election tomorrow. His friends have told him to change everything from the color of his tie to the way he smiles.

He has made some concessions. He now prefers to use a microphone so there is something to do with his hands, which before always looked like they were searching for suitable employment. And programs he once graciously credited to the General Assembly as a whole are now referred to as his initiatives, with Cardin often speaking of himself in the third person to drive home the point.

But essentially, with Cardin what you see is what you get: a politician who gets a gleam in his eye when talking about the state budget.

"I've made a commitment I want to be elected governor a certain way," he said. "If I can't get elected that way, then I take that risk. I'm not going to be something I'm not."

A year before the Democratic primary, Cardin's battle is with the insiders, whom he calls "the 5 percent," the money people and opinion leaders who shy away from betting on long shots. That is the group he has been trying to crack this summer, staging a dozen Speak to the Speaker forums around the state designed to enlarge the circle of those who think he is the best of the candidates for governor.

But every step of the way he has been haunted by a phantom named Schaefer, who will probably raise more than $1 million next month at a fund-raiser that is to proclaim what the mayor is already saying to everyone except the media -- that he is a candidate.

Conventional wisdom holds that Cardin, a politician with a Baltimore base, cannot survive in a race with the enormously popular mayor of that city. "He's going to hang in until the mayor announces, and once the mayor's in he'll walk," said one prominent Democratic fund-raiser, a view that is widely shared.

Cardin's stock answer is that his campaign "is not contingent on what any other candidate does."

Admitting with a laugh that he may be "the last person in Maryland" who believes that Schaefer will not be a candidate, Cardin says that even if the mayor does run, it will not automatically doom his own campaign. If he can keep raising money, and if the polls show he has a chance, he will stay in the race regardless of what Schaefer does, he says.

Cardin, who says he does not "mind" running against Sachs, has no illusions about Schaefer's strength. "On everybody's polls, he's off the charts," said Cardin. "Don has a mystique about him. People feel he's performed magic in Baltimore. But there is a great deal of difference between being a successful mayor of Baltimore and a successful governor. Don Schaefer knows that."

Fund-raising head to head with Schaefer will be the true test of Cardin's political stamina. Cardin has raised about $500,000 of the $2 million he estimates he will need, the bulk of it at a large fund-raiser last winter. Within the last few weeks, he has begun another cycle of raising money, one that competes directly with ticket sales for Schaefer's Sept. 26 fund-raiser in Baltimore.

There has been considerable speculation that Cardin will run for Congress, talk fueled by increasing signs that his district's congresswoman, Barbara Mikulski, will run for U.S. Senate, and by the fact Cardin has a separate campaign committee for corporate contributors who cannot give to federal campaigns. It has also been said that Cardin will run for attorney general, or settle for the Maryland treasurer's post so he can stay visible until the next opportune time to run for governor.

Cardin rules those choices out. He will not run for Congress. He does not want to be treasurer. His priorities, he says, are governor first, private life second, and eventually returning to the House of Delegates third.

Cardin's determination to remain in the race despite the odds may ultimately pay off, according to one minority theory making the political rounds. That school of thought predicts that Sachs and Schaefer, whose mutual antipathy is well known, could engage in such a vicious dogfight that the electorate will turn elsewhere in disgust.

These theorists point out that Harry Hughes was a dark horse when he first ran for governor until a couple of weeks before the 1978 Democratic primary.

Cardin said that if he can survive until the next legislative session ends in April, "I'll be the next governor." In the meantime, he said, "I want to talk about correctional reform. I want to talk about higher education. I want to talk about how you manage the budget in Maryland. I want to talk about process."