Four years ago, when underdog Harry Hughes asked his old friend, State Sen. J. Joseph Curran Jr., to be the No. 2 man in his campaign for governor, Curran turned him down. "Harry," he said, "you are my dear friend, but my gut tells me you can't win this race."

Like many people in 1978, Curran was wrong about the Hughes candidacy. Four years later, incumbent Governor Hughes again approached Curran about being his running mate. This time Curran said yes. "It was an entirely different offer than last time," said Curran, who today officially became Hughes' running mate.

"Last time, the question was, did you want to get into this campaign, do that kind of work and hope?" Curran said the other day, picking at a crabcake in a Harborplace restaurant where the second of his four children works as a waitress. "This time, the question was, do you want to be lieutenant governor? Because as sure as day follows night, Harry Hughes is going to be reelected."

The 1978 offer came in Curran's back yard and it came out of the blue. The 1982 offer came on the governor's yacht and was at least as much of a surprise as the one four years ago.

"Harry called me up on a Friday afternoon and asked me if we (Curran and wife Barbara) wanted to go out on the boat the next day," Curran said. "I figured he was inviting 10 or 15 senators and their wives out for a day. But it turned out to be just the four of us (Hughes and his wife Patricia).

"Just before dinner Harry and I were talking and he asked me if I would be interested in running with him. I was stunned. Then he told me that his polls had shown I had good name recognition and could probably help the ticket."

Curran told Hughes he would talk the offer over with his wife. He also remembers mentioning to Hughes that perhaps a fiscal expert, someone like Speaker of the House of Delegates Benjamin L. Cardin, might be a more apt choice.

That suggestion was typical of Curran. He has been in the legislature for 24 years, the first four in the house, the last 20 in the senate. By nature he is gentle and self-effacing, aware of his capabilities but also cognizant of his weaknesses.

A few days after the meeting on the yacht, Curran went to the governor's office to tell him he would be willing to join the ticket.

Curran said yes, not because he covets the state's No. 2 executive position, but because he saw becoming a full-time lieutenant governor as a means for changing his lifestyle, one that has forced him to work most weekends trying to juggle his law practice here with his Annapolis responsibilities (he has been chairman of the judicial matters committee for 16 years).

After accepting, Curran waited.

For a month his name was mentioned as the front-runner. For a month Hughes and his staffers kept insisting others were being considered. Finally, in the last 10 days, Hughes began romancing Cardin. The two men performed a political you-ask-me-first dance until Wednesday when Cardin called Hughes and took himself out of the running.

Curran was philosophical while waiting for the phone to ring. "If it happens, fine, it would be nice," he said. "But if it doesn't, well, maybe that's the best thing for me anyway."

Curran is from the upper middle class Roland Park area of Northeast Baltimore, the heir to a political heritage that began with his father, a two-term city councilman. The Curran name long has been linked with progressive politics and an endorsement from their political club has always been considered a prerequisite for success in the district. Curran's brother, Mike, is a councilman now and cousin Gerald is a four-term member of the House of Delegates, who will probably seek Joe's seat.

Curran is not an eye-catching politician. He dresses conservatively, his graying hair combed high on his forehead. He has an easy smile and never seems to raise his voice even when speaking emotionally.

"If I have any real ambition to move out of the senate, I would be more inclined to move to the federal level anyway. I've always thought that if I went to Washington I could make a difference. It seems no one down there has ever really tried to start a grass-roots peace movement to say, 'Okay, enough is enough, let's really find a way to stop all this.'

"I know that may sound corny or like a dreamer or something but that's the way I feel. I could be a real zealot about it. I hear people talk but I've never really seen a single senator who has devoted himself to that. I honestly believe that if you start with your own constituency and build on that you can make a difference because I don't think the average Russian or the average Chinese wants to go to war any more than we do.

"I think there's a small group of generals who feel they have to rattle swords to stay in control and the rest of us are out here scared we're going to get blown up someday. Why not go to war against war?

"It just seems like nobody says beans. Nobody said (Lyndon) Johnson was wrong. Why do the rock stars have to be the ones out front doing all the screaming? Why are politicians always sitting back waiting to see what the polls say instead of standing up and saying, 'This is right and this is wrong.' You don't need a poll to figure that out.

"I enjoy state government. I could enjoy being lieutenant governor, but in Congress it would be different. With me, those issues are visceral."

Curran has felt that way for a long time. In 1967, before the antiwar movement took wing, before Gene McCarthy's moral victory in New Hampshire, Curran, then 35, ran for Congress as an antiwar candidate.

"I just sat there watching the 6 o'clock news every night and they were reading body counts like the Dow Jones average," he said. "They would say that 2,000 Vietcong were killed and only 300 marines, wasn't that great? It was like a statistical competition. I decided to stand up and say something about it."

Curran lost that race, narrowly.

The year before, with the help of Harry Hughes, he became chairman of the state senate's judicial matters committee. Hughes left the senate to become state secretary of transportation, but the two men remained friends.

As lieutenant governor, Curran says he would like to concentrate on his area of expertise--the judiciary system.

"I'm not an expert on the budget so why should I try to do the budget?" he said. "I think I could make a contribution trying to make the courts work better and to make our prison system better. I think that's the weakness in our system, the prisons. The police, the state's attorneys, the judges are doing their jobs. But they see these guys a couple hours, a couple days. Then they sit in prison doing nothing for eight, 10 years and come back out meaner than when they went in. We have to change that. You can't do it in a day or a week but you can do it."

Because Curran does not breathe political fire, some of Hughes' detractors have tried to label him another Sam Bogley. "That's just ridiculous," said one Hughes staffer. "The two men (Curran and Bogley) have nothing in common ideologically and Joe has proven his competence as a committee chairman for 16 years."

Even Del. Paul E. Weisengoff (D-Baltimore), political protege to Hughes' primary opponent, Sen. Harry J. McGuirk (D-Baltimore) and one of those who raises the Bogley comparison, concedes, "you really can't say anything bad about Joe Curran."