State Sen. J. Joseph Curran Jr. of Baltimore has emerged as the leading contender to be the running mate of Maryland Gov. Harry Hughes, sources close to Hughes and Curran said yesterday. Hughes will formally announce his candidacy for reelection Tuesday and is expected to name his candidate for lieutenant governor two weeks after that.

The governor, who is dropping Lt. Gov. Samuel W. Bogley from the ticket after a stormy four-year relationship, has met with Curran twice in the last two weeks to discuss the No. 2 spot on the Democratic ticket. The first time was over dinner with both men's wives present. The second time was Monday in Hughes' office. At that second meeting, Curran told Hughes he would accept the job if it were offered.

Hughes contacted Curran, according to sources, after it became apparent that his top two choices, Baltimore County Executive Donald B. Hutchinson and House Speaker Benjamin L. Cardin, were not interested in the No. 2 job.

Curran is one of Hughes' oldest political friends, having served in the state Senate with him, and he shares many of Hughes' political views, including gun control. Curran was one of the first elected officials to publicly support Hughes' long-shot candidacy in 1978.

Curran's presence on the ticket would give Hughes a firmer political power base in Baltimore, where the likely Republican nominee, Anne Arundel County Executive Robert A. Pascal, has been trying to make inroads. Curran comes from one of the city's oldest political families, his father having been chairman of the City Council and his brother being a present member of the council.

A Hughes spokesman said yesterday that Curran is one of several people under consideration to replace Bogley.

Others who have been considered as a running mate include State Treasurer William S. James; Secretary of State Fred L. Wineland; Del. Nancy K. Kopp (D-Montgomery) and former HUD assistant secretary Robert Embry.

But Curran, 50, a five-term senator, is the clear leader now. Curran, chairman of the Senate Judicial Proceedings Committee, confirmed yesterday he had discussed the situation with his wife last week before telling Hughes Monday he would be interested.

"I'm honored to be considered," Curran said. "I assume the governor is talking to other people about the job too. This came completely out of the blue. I've been planning all along to announce for reelection on June 5.

"I really had to sit down and think about making that kind of change. I've got a very active law practice and I wasn't sure if I wanted to give that up."

The lieutenant governor's salary is $52,000 a year, which Curran said is considerably less than his combined lawyer-Senate earnings. But the salary will go to $62,000 beginning next year, which Curran said is much closer to his income.

Curran was elected to the House of Delegates in 1958 and served one term there before being elected to the Senate. He is a Catholic, a factor sources said was taken into consideration because Pascal is Catholic. Additionally, Hughes wife Patricia and Curran's wife Barbara are friends, a direct contrast to the relationship between Mrs. Hughes and Bogley's wife Rita, who openly disagreed with the Hugheses over their prochoice stand on the abortion issue.

Curran was contacted by Hughes after attempts to persuade Hutchinson to join the ticket failed. According to sources close to Hutchinson, the county executive was pressured by the Hughes people until just before he announced his candidacy for reelection on May 4.

Cardin, whose relationship with Hughes has been rocky at times, but improved during this year's legislative session, was sent feelers by Hughes' staff but did not respond to them.

Hughes will make his formal announcement next week in Towson and at the Sheraton-Lanham Motel in Prince George's County. He has two opponents in the primary, Sen. Harry J. McGuirk (D-Baltimore) and Ocean City Mayor Harry Kelley. McGuirk said yesterday he was "close" to picking his running mate and expected that he or she would come from the Washington area.