In his first U.S. Senate campaign Paul S. Sarbanes was so absorbed by detail that he ordered aides to change the way the "S" was printed on his billboards. He insisted it "wasn't strong enough."

In his dealings with Senate staff, Sarbanes is notorious for asking questions so obscure that sometimes the staff doesn't think answers exist.

In six years in the House, he was usually the "undecided" on the Maryland delegation's weekly voting report to the leadership. He was waiting to get more information.

"If the decision came down to whether the marigold was going to be the national flower," said one old friend of the freshman senator, "Paul Sarbanes would not be able to vote, he'd be so worried about what the Shasta daisy people were going to think."

Maryland's Democratic senator wants every fact and detail, every chance to think and think again before making a decision. Admirers laud this as a style of careful reflection, while critics call it paralyzing indecision. Sarbanes' own view is that the public wants "leaders who are not rash or impulsive, who want to have all the facts . . . before they make a decision."

The senator, said a former aide, is a brilliant man who "is always very deliberate in a town where people shoot from the hip."

It makes him an unlikely politician, but there is a lot that's unlikely about Paul Spyros Sarbanes. He is a lawmaker who seldom introduces legislation, a candidate who eschews long campaigns and a public official who shuns publicity.

Twenty months ago, the mild-mannered senator was thrust unwillingly into the spotlight when the National Conservative Political Action Committee NCPAC picked him as its number one target for defeat. Condemning him as "too liberal for Maryland," the right-wing group went after Sarbanes with a vengeance and $625,000 worth of commercials.

Supporters now say the attack was the best thing that ever happened to him. It galvanized his friends and divided his foes. It forced the reluctant campaigner onto the campaign trail, and enlivened his ponderous speeches. It drew support and contributions from people around the country who were still angry about 1980, when NCPAC helped extinguish several of the Senate's liberal lights.

Instead of leaving Sarbanes savaged, the NCPAC campaign left him with a comfortable lead over his Republican opponent, Prince George's County Executive Lawrence J. Hogan, according to recent polls.

"I'm convinced that God wants Paul Sarbanes in the U.S. Senate," said Maryland state Del. Gerard Devlin, a longtime admirer. "Here you have a guy with only one real problem: He's almost reclusive as politicians go. Then NCPAC comes along and suddenly he's a national figure. The Lord works in strange and mysterious ways."

These days when the 49-year-old Sarbanes appears at Democratic rallies, he is a hero. At a bullroast sponsored by the Maryland AFL-CIO, state attorney general Stephen Sachs, echoing the words of Democrats across the state, told the crowd, "I don't think there's an election, including my own, that's more important than the reelection of Paul Sarbanes." The union members ate it up, as do audiences of working people everywhere Sarbanes goes.

"I believe in opening up the ladders of opportunity," Sarbanes told an applauding audience of teachers in Baltimore recently. "I want people to climb those ladders of opportunity. But I don't want them knocking them down so nobody else can follow."

Reagan's "trickle-down" economics is doing just that, Sarbanes charged, turning America away from a "vision of fairness and opportunity."

It is this theme of the American dream that Sarbanes frequently sounds, perhaps because he has lived it himself.

Sarbanes grew up in the 1930s above the little restaurant his family ran in the small Eastern Shore city of Salisbury. His father was a Greek immigrant who came to America at 15, not knowing a word of English. The father revered books, hard work and Franklin D. Roosevelt. The son inherited those tastes.

As a boy, he waited on tables and washed dishes. He became a top student and star basketball player, and his academic prowess propelled him first to Princeton, then to Oxford on a Rhodes scholarship and finally to Harvard Law School. Wherever he went, he graduated with top honors.

Sen. Richard Lugar (R-Ind.), who traveled to England on the Queen Elizabeth with Sarbanes and other Rhodes scholars in 1954, remembers that Sarbanes was always conscious of his roots. In the rarified atmosphere of Oxford, Sarbanes was forever pointing out the trappings of power and privilege, Lugar recalls. "I remember when we went to some sporting event, Paul made a comment that he empathized with the person selling refreshments . . . . He was that fellow selling popcorn or whatever to the people in the boxes, not the people in the boxes who were buying."

Sarbanes carried that set of values from the Eastern Shore to the Maryland legislature in Annapolis and finally to Capitol Hill. And he has never wavered from his quiet, meticulous style. "In the House of Delegates, he'd get the state budget and take it home and study it, night after night," recalls a colleague who knew him there in the late 1960s. "Then he'd stand up and make the most magnificent speech on it, a slam-bang budget analysis. After that, you wouldn't hear from him on the floor for the rest of the session."

Sarbanes stayed in the General Assembly for just one term. In 1970, he entered the Democratic primary for Congress in Baltimore, defeating Rep. George Fallon, a 13-term incumbent thought to be unbeatable. Six years later he ran successfully for the Senate, crushing former senator Joseph D. Tydings' comeback chances in the primary and then swamping incumbent Republican Sen. J. Glenn Beall.

Sarbanes' reputation as a brainy liberal was enhanced as a result of his roles in the 1974 Nixon impeachment hearings and the 1978 debates on the Panama Canal treaties, and his unremitting opposition to the Reagan tax and budget programs. Despite a Senate voting record that last year earned him a 95 percent rating from the Americans for Democratic Action and 100 percent from labor, Sarbanes hates such "pigeonholing labels" as "liberal."

He prefers to say, "I generally align myself with the working people. I am essentially on the side of opening up opportunity in the country and maintaining it."

No one questions his adherence to those principles, or his brilliance. "There are few people around in the Senate who are his intellectual peers," Sen. Paul Tsongas (D-Mass.) said, reiterating the comments of many.

But some on the Hill question what Sarbanes is doing with all his brains and ability. "When an issue comes up and we do a head count, Sarbanes will be among the 15 or 20 we count on," said an aide to another liberal senator. "Sarbanes will vote with you, but he'll seldom make a speech. He's never out in front on an issue."

Challenger Hogan calls Sarbanes a "do-nothing senator" with "a pitiful record." Since Sarbanes joined the Senate in 1977 he has introduced 22 bills. By comparison, in 1981, the 100 senators introduced 2,005 bills, an average of 20 each for one year.

Sarbanes responds that he never regarded "this game of popping in legislation and issuing press releases as the real substance of legislating." A senator, he believes, can exert more influence by working to shape major legislation in committee.

But even on his two committees, Sarbanes is viewed as a quiet sort of Democratic teamplayer. This year, though he attended all of the Banking, Housing and Urban Affairs Committee work sessions, where legislation is amended and passed, he rarely took an active role. When he did, it was to support other senators' amendments on bills such as one to stimulate the stagnant housing industry. Sarbanes attended six of the 17 major hearings the full committee and his subcommittees held this year.

On the Foreign Relations Committee, Sarbanes again attended all the work sessions, but made it to only four of 15 major hearings. When it came to determining the amount of foreign aid for Israel and keeping a balance in military aid to Turkey and Greece, Sarbanes was there strongly arguing his case. But on other major issues, such as President Reagan's Caribbean Basin Initiative, other Democrats put forth amendments while Sarbanes remained on the sidelines.

"Frankly," said Sarbanes, "this is not the year I would have commended you to look at. We've been under political siege for 18 months." He asserted that he has played an active behind-the-scenes role this year in legislation important to savings and loans. In 1981 he voted in nearly 98 percent of the Senate roll calls, and this year he made close to 90 percent. "I've continued to do my work and do it well. But NCPAC thrusts people into political campaigns far sooner than would otherwise be the case," he said.

In previous sessions, Sarbanes was more active, helping shape major urban development programs and legislation that blunted the effect of the Arab boycott of Israel by making it illegal for American businesses to comply. In the days of the Democratic majority, Sarbanes said, "I was a subcommittee chairman and I was active in discharging my job. A lot of things were my initiatives."

Perhaps this goes to Sarbanes' strong sense of apprenticeship and staying with the assigned job. "I sometimes say to him, 'Why don't you speak out about this thing or that?' " said his wife, Christine. "And he says, 'I'm not on that committee. It wouldn't make any sense.' "

Sarbanes' old friend, Montgomery County Executive Charles Gilchrist, said that on issues where the senator does grab hold, "opponents have found out to their dismay that he's extremely determined, single-minded in pursuing a goal. Someone once said he stalks his opponents, not in the sense of being a predator, but he has this inexorable way of moving ahead. He never gets deflected."

The trait has been apparent several times during his career.

In 1974, Sarbanes, with his current opponent Hogan, was a member of the Judiciary Committee that voted to impeach Richard Nixon. Though the first article of impeachment was the work of a coalition of centrist Republicans and southern Democrats, Sarbanes was the point man when the committee debated the article before a television audience of millions. When the committee adopted its first historic charge against Nixon, it was called the Sarbanes article.

"No question he made his big name with the '74 Judiciary Committee hearings," said one Senate aide. "Here was this clean, upstanding man who came across as fair with Nixon and saddened by events. And that propelled him into the Senate."

Once there, the scholarly and sober Sarbanes found the perfect match for his talents: the 1978 debates over the Panama Canal treaties. His wife remembers him dragging home huge portfolios of research material until they all but filled the tiny second-floor study of their Baltimore home, from which he commutes daily.

While most senators were lining up for or against the treaties, Sarbanes, true to form, waited until the last day of the committee hearings to announce that he favored them. When the floor debate began, the freshman senator stood side-by-side with his senior colleague, Sen. Frank Church (D-Idaho), to defend the treaties against conservatives who attacked them as a "giveaway of the canal." When ratification came by a dramatic one-vote margin, Sarbanes came in for a large share of the accolades. "You've won your spurs in this debate," Church told him.

Those spurs have been used seldom since then. Only once last year did he leap from the pack, during the confirmation hearings on Alexander Haig, President Reagan's choice for secretary of state. Sarbanes relentlessly pressed Haig, who had served as White House chief of staff for the final months of the Nixon administration, to make "value judgments" about the abuses of the Watergate era.

Dissatisfied with Haig's responses, he was one of the two senators who voted against the nomination in committee and one of six who did so on the floor.

A few months later, Sarbanes was one of just 10 senators to vote against the 1981 budget reconciliation -- the opening move in Reagan's economic game plan.

The risks of such lonely stands, at a time when Ronald Reagan was riding high, seem uncharacteristic for the ever-cautious Sarbanes.

He doesn't see it that way, however. "I've taken a lot of chances in my political life . . . . Look at the political risks we've taken," he said, harking back to his first longshot race for Congress.

"I would not describe these things as out of character. Maybe it just means I'm a lot more complicated than people think."