When Maryland Gov. Harry Hughes selected state Sen. J. Joseph Curran Jr. as his running mate two week ago, one of the major reasons for the choice was Curran's perceived ability to unite Baltimore Democrats.

But on the very afternoon that Hughes introduced his new partner, he was faced with the possibility that a political war might break out in Curran's own district. Moments after Curran formally announced that he would vacate the senate seat he has held in Northeast Baltimore for the last 20 years, two of the delegates from his district, Gerald J. Curran and John A. Pica Jr. retired to Curran's office to discuss their political futures.

Curran, Joe Curran's cousin, a four-term delegate, wants to run for the senate seat. Pica, a one-term delegate and the son of a former city councilman, wants to run for the senate seat.

So they talked.

"He was very determined," Pica remembered. "He said he had waited a long time for this and he thought it was his time.

"Johnny was friendly, warm and firm," Curran said. "We shook hands and went in different directions."

Those different directions, creating the potential for a gloves-off fight within Joe Curran's own organization, The United Third District, has created enough concern in Annapolis during the last two weeks that members of Hughes' staff now are involved, trying to get Gerald Curran out of the race.

"The last thing in the world they need is a bloodbath in the Northeast," said one legislator. "And that's what Pica-Curran would be."

The Northeast is important to Hughes, especially in the Democratic Primary where he will face Baltimore Sen. Harry J. McGuirk. McGuirk should do well in his own south Baltimore District and the Hughes people would like to run just as well in Curran's district.

"Peace is a great thing," said Gerald Curran, who must make a decision by the July 6 filing date whether to run back for the house or for the senate.

"Obviously, it's the ideal, but this isn't utopia. I really don't buy the idea that a race between Pica and I would split the district," he said.

Others do. Ideally, Hughes and Joe Curran would like to see the younger Curran run for another term in the house.

Gerald Curran, 43, currently is vice chairman of the Constitutional and Administrative Law Committee.

If he believed he would become a chairman in the house next year, Curran would probably drop out of the senate race.

So, the negotiating began. Hughes' people always have maintained they do not make deals, but Curran has talked with Hughes legislative liaison John F.X. O'Brien this week to find out what role, if any, the Hughes people might be willing to play in making peace.

"The governor might talk to Gerry and, as the leader of the Democratic Party in the state, ask him to run for the house," said a Hughes staffer.

"He might tell him it would be a sacrifice that would be remembered," the Hughes aide said.

"Gerry Curran is a valuable member of the leadership in the house," Cardin said. "But right now I don't feel any need to change any of my chairmen."

This has been a difficult year for Curran. Of 188 members of the legislature, he may have been tossed back and forth during the various steps in redistricting more than anyone.

Since January, he has been moved from the 43rd Congressional District to the 44th District and finally, on June 5, back to the 43rd -- which was where he wanted to be.

While Curran was temporarily in the 44th, Joe Curran, Pica and the third delegate from the 43rd, Henry R.(Bobby) Hergenroeder, also a four-term member, began making their plans to run as a slate. When Hughes made his offer to Joe Curran, Pica immediately began telling people he would run for the senate.

At 30, Pica is aggressive, ambitious and organized. With his dark good looks, his Italian heritage and an Irish Catholic wife, he is the prototype candidate for the district.

In 1978, running independently, he ran first in the delegate race.

"Johnny Pica is a formidable candidate," said Joe Curran, "regardless of who he runs against."

The day after Curran and Pica talked, Curran had lunch with Hergenroeder. Since the two men go back 16 years together in the legislature, Curran expected Hergenroeder would be with him automatically. But Hergenroeder wasn't about to make any commitments.

Two days later, Curran received another shock when he talked with James Lacey, an influential party leader, about support.

Lacey categorically refused to help Curran, saying he would run against Curran himself before he would support him.

Curran retreated after that, going underground for several days. Last weekend he met with his cousin to discuss the situation. "He told me if I ran he would support me," Gerry Curran said. But friends of Joe Curran add that the senator at the same time told his cousin he thought he should seriously reconsider.

The next night Curran surfaced at a candidate's forum. "I'm running," he said, "for the legislature."

One Baltimore politician familiar with the Hughes administration predicted that a Curran-Pica war will be averted. "Harry Hughes has never gotten involved in local politics, even when people have gone to him asking for help," he said. "He won't do it this time either. But he's going to get lucky. It would be a financial risk for Gerry Curran to run for the senate. So, some phone calls will be made and in the end, Curran will be able to say that the governor and Cardin want him in the house leadership, so he's going to stay there."

And, if not?

"Then the Hughes-Curran ticket has a problem."