An act of heroism, by definition, involves taking risk. These days, Bruce Laingen, who once played the role of an American hero, is trying to decide whether to run the risk of casting himself in what can often be a most unheroic role: political candidate.

Specifically, Lowell Bruce Laingen, the most visible of the 52 American hostages released from Iran one year ago, is trying to decide whether to challenge Paul S. Sarbanes (D-Md.) for his seat in the U.S. Senate.

Laingen's appeal to Maryland Republicans has little to do with ideology or political credentials. In fact, many of those urging him to run admit they know little about where he stands on any of the issues. But like many others who have first attained fame outside politics, Laingen has some of the basic ingredients inherent in political success stories, including instant name recognition and a fresh record that cannot be attacked by any opponents.

This appeal is often ascribed to athletes, Rep. Jack Kemp of New York being one example, Sen. Bill Bradley of New Jersey being another. As the current occupant of the White House proves, it can also be found in actors. Finally, there are heroes, men like astronauts John Glenn and Harrison Schmitt who are both now in the U.S. Senate.

Laingen is a different kind of hero, unique in fact. He was a captive, part of an emotionally wrenching ordeal that ended with a cathartic clap which brought chills to spines and memories that still linger. Those kinds of feelings can potentially transcend partisan party politics, and in Maryland, where a Republican must get Democratic votes to be elected, that can be extremely important. Memories and Laingen's appeal as the modest, "thank-you and God-bless-you America" spokesman, is what the Republicans would like to market in Maryland.

If there was a moment when Laingen became a marked man in political circles it was last Jan. 28 when he spoke to President Reagan and the nation on behalf of the former hostages at the White House. For much of the 444 days the hostages were held in Iran, Laingen, the charge d'affaires, was their link to the outside world through phone calls to his wife Penne. When they returned he continued as spokesman. His easy smile and soft manner impressed people; his simple eloquence seemed just right for the occasion. Soon after his White House speech his name began to make the rounds on the never-ending Maryland rumor circuit.

Laingen, 59, said in a brief interview recently that he has not made any decisions yet. He refuses to even discuss the situation in much detail because, as a federal employe covered by the Hatch Act, talk of political ambitions could jeopardize his job as vice president of the National War College at Fort McNair.

But quietly, Laingen is taking the necessary steps. Early last month he registered in Maryland for the first time, as a Republican, giving up the independent status he had maintained in his native Minnesota for years. He has willingly accepted speaking invitations around the state, most recently giving a talk on U.S. foreign policy at a high school in Harford County.

"You don't make that kind of trip to a small school in the northern corner of the state at this time of year just out of a sense of duty," said George Wills, a Baltimore Republican who is one of the more vocal Laingen supporters in the state. "At the very least it indicates a definite interest."

Within the next week or two, Laingen will have to decide whether to accept a number of invitations to speak at several of the traditional Lincoln Day dinners, generally regarded as early forums for party candidates.

Maryland Republicans are watching Laingen closely and waiting anxiously. Many party leaders and workers would like to see him in the race because they see him as their best chance of beating Sarbanes.

Laingen has been a career diplomat, having twice been a deputy undersecretary of state. He was ambassador to Malta and, according to foreign service sources, was assigned to Iran because he was considered a tough man for a tough job. "Don't let the low-key approach fool you," said one former colleague. "There is never any doubt about who the boss is when you work for Bruce Laingen."

Former colleagues describe Laingen as a "straight-arrow," a man who rarely raised his voice in dealing with subordinates. Why would he run for elective office? "When you are a career diplomat you are constantly surrounded by politicians," said another former hostage who has worked with Laingen. "If you are as bright as Bruce is you are bound to be interested in the phenomenon and you are likely to believe you could be successful at it."

Since diplomats must always maintain political neutrality, at least in the public realm, there is no Laingen for other politicians and voters to consider. But he is regarded by most who know him as a moderate, a man who reportedly considered registering as a Democrat in Minnesota at one point in his life although his wife has been a registered Republican in Maryland for many years.

At the moment, there is only one announced candidate for the Republican nomination, V. Dallas Merrell of Silver Spring. Lawrence J. Hogan, the Prince George's County executive is expected to formally announce his candidacy today. J. Glenn Beall Jr., the former senator, has said he might run.

It is the presence of Hogan, and the likelihood that he would emerge from the primary as the candidate, that has some state Republicans thirsting for a Laingen candidacy. Hogan is known as an excellent campaigner, hardnosed, uncompromising. But he has had a tendency to make as many enemies as friends, especially during his often stormy three years in Upper Marlboro.

"With Larry Hogan we start out with a whole bunch of negatives," one party official said. "With Bruce Laingen we start out with no negatives, great name recognition and the potential to really build on his positives. Even if we go backwards with him, we'll probably just end up where we would be with Hogan."

Still, the very thing that seems to make Laingen so attractive to the Republicans--his lack of a record that can be attacked by an opponent--is also the biggest stumbling block for Laingen should he choose to run.

"Most of us perceive him as a moderate," said Jeannette Wessel, one of the leaders of a "Draft Laingen" committee that is in the formative stages. "But to be honest, we really don't know where he stands on most issues. And, since we've been advised by our lawyers not to contact him because of Hatch we can't get any answers. That makes it kind of tough."

Most view Laingen's political inexperience as a plus. But some party regulars point out that an untested candidate is just that and could fail miserably under the pressures of a campaign. "You never know if a guy has got it until he gets out there," said one. "He might make some horrible mistake. We just don't know because we don't know him."

Beneath the talk about Laingen's views, about his experience, about his personal qualities which all the Laingen supporters describe, is a basic reason for supporting a Laingen candidacy: many Republicans think he can do what Hogan and Merrell can't--beat Sarbanes in November.

"There is a good deal of movement in the state for Laingen," party chairman Allan Levey said. "We think Paul Sarbanes is vulnerable and beatable. Any of the candidates could win. A lot of people think Bruce Laingen might do very, very well."

"I think Bruce would be a superb candidate," said Paul Clark, head of the Republican Central Committee in Montgomery County. "I think he, Hogan and Merrell would have a very close primary. And I think if Bruce won he would be an extraordinarily capable opponent for Sarbanes who is vulnerable."

Clark admits that he knows Laingen only by reputation, but he is pragmatic about the qualities Laingen would bring to a campaign.

"He's got name recognition right away, he's come across to people very well in the past. True, people may not know where he stands on some issues because he hasn't been in politics before but people like John Glenn and Harrison Schmitt overcame that. So did George Murphy and Ronald Reagan. Let's face it, the issues that count most are the ones that come up during the campaign."

Laingen has one other thing going for him: it might be difficult for any opponent to attack him. That could present a unique problem for any candidate, especially Hogan, whose campaign style in the past has often been compared to blitzkrieg.

Hogan will not comment on how he would deal with a Laingen candidacy. His press aide, Larry Hogan Jr., said last week that the Hogan campaign plan included, "some minor adjustments," with Laingen in the race, but added: "Our plan doesn't include Laingen because we don't expect him to run.

"But, it is fair to say that a candidate who has never been in a campaign before presents different problems because he has absolutely no negatives."

Those who know Hogan see him having a difficult time against Laingen, partly because of Laingen's image, partly because of his lack of popularity with many Republicans in the state. "Larry knows he would have serious problems with Laingen so he's trying to scare him off now," said one former member of Hogan's administration. "He's running around the state trying to look so solid Laingen won't get in."

Merrell, the longshot candidate, says he doesn't think Laingen will get into the race. But, he concedes that, "being a former hostage certainly gives him sex appeal."

If Laingen were to win the September primary, his opponent would be Sarbanes who says that right now the candidacy or noncandidacy of Laingen is "something they the Republicans have to sort out on their own side."

His staff and supporters say they would have no problem running against Laingen. "We don't even know what kind of person he would be politically," said Pete Marudes, head of Sarbanes Baltimore office. "We don't know if he would or would not be a presence in the state. The only thing we do know is that he would be carrying the Republican banner and all that that means."

Wessel, Levey and others say there is no reason for Laingen to formally announce now, especially since it would mean giving up his job. "I would hope that once we get started, we can put together a presentation to show to him within 60 days," Wessel said. "That would be April and if we've got an organization going by then that would be plenty of time to announce."

The Lincoln Day dinners bring a certain urgency. They begin early this month, and by agreeing to speak at them, Laingen would almost be announcing his candidacy. "Clearly," he said wryly, "I have to make a decision on them soon. It's fair to say, I'm trying to think this decision through quite thoroughly."

Laingen would not be drawn into a discussion as to where he stands right now. But, when asked if he might describe himself as not opening the door to let his supporters in but also not telling them to go away either, Laingen answered quickly.

"That," he said, "is an excellent way of putting it.