ANNAPOLIS (AP) - Anthony Brown, a black legislator from Prince George's County who is considered a rising star in the Maryland Democratic Party, will run for lieutenant governor next year with Baltimore Mayor Martin O'Malley.

The deal was sealed Wednesday night when Brown and his family joined the O'Malleys for dinner at the mayor's home, Jonathan Epstein, O'Malley's campaign spokesman, said Thursday. The formal announcement will be Monday in Prince George's County, a key battleground in next year's gubernatorial election.

Brown, 44, now in his second term in the legislature, considered running for attorney general next year. But incumbent Democrat J. Joseph Curran, who is O'Malley's father-in-law, has not said whether he will run again. Brown said he decided to accept O'Malley's offer after discussions with the mayor, his family and "people whose opinions I value."

"I believe that in partnership with Mayor O'Malley, I will be able to make a greater difference in a positive way on behalf of Marylanders," Brown said.

Brown would not discuss what his duties might be as lieutenant governor, but said that "my willingness to serve as lieutenant governor in an O'Malley-Brown administration is based on my firm conviction that there will be a full partnership between me and the mayor."

Brown said he was attracted to O'Malley because of the mayor's "passion for public service."

"I feel that energy," Brown said. "I sense that purpose that he has, and I share it."

Gov. Robert Ehrlich and Montgomery County Executive Doug Duncan, who is challenging O'Malley for the Democratic nomination, have not chosen running mates.

Brown, a lawyer and the father of three young children, brings an impressive rsum to the campaign and also adds racial and geographic balance to the ticket.

Brown is a cum laude graduate of Harvard University and of Harvard Law School, is majority whip in the House of Delegates and is a lieutenant colonel in the Army Reserves. He volunteered to go to Iraq last year and spent 9 1/2 months there, missing the 2005 session of the General Assembly.

Brown is not well-known outside his home county. But Donn Worgs, an assistant professor of political science at Towson University, said he is, on paper, a good addition to the ticket.

"You've got the geographical balance you want. You have someone who in theory would appeal to African-American voters," Worgs said. "Being a veteran, his political experience, he seems like someone who can have broad appeal."

Donald Norris, a professor of public policy at the University of Maryland, Baltimore County, said by choosing Brown, O'Malley appears to have avoided a mistake that hurt the gubernatorial candidacy of Lt. Gov. Kathleen Kennedy Townsend four years ago. Townsend made a surprise choice of a white Republican, retired Adm. Charles Larson, as her running mate.

"When Kathleen went out of party and didn't even talk to people within the party, and certainly didn't talk with African-American political leaders, she was heavily criticized," Norris said. "This avoids that kind of criticism."

Curt Anderson, a Democratic legislator from Baltimore who is an O'Malley supporter, said he was "ecstatic that they picked Anthony Brown."

"I just think he represents all the good things that our party is about," Anderson said. "He and Martin will be able to energize some of these Democratic voters, these folks in their 20s and 30s, who are looking for that kind of leadership. I just can't imagine a better choice for lieutenant governor."

O'Malley agrees.

"I'm really excited about the opportunity to govern with someone of Anthony Brown's integrity," O'Malley said at an event Thursday where he announced plans to invest $75 million in school construction. "I can't tell you how happy I am that he was willing to do this tough job. I could not be happier in the lieutenant governor candidate that we've been able to recruit."

O'Malley described Brown as a person of public service, commitment and good character who understands policy very well.

"This ticket reflects the diversity of the state," said O'Malley, adding that he interviewed a number of people before making his choice. "And at the end of the day, Anthony's grasp of the issues, relationships with the legislature, respect in Prince George's County, all made Delegate Brown the right choice for moving our state forward in the important role of lieutenant governor."

Duncan said in a statement issued by his campaign staff that he likes and respects Brown, but "the choice Democratic primary voters face is not about lieutenant gubernatorial candidates, since we are sure Martin O'Malley will be friends with and respect Doug Duncan's running mate as well." Duncan has not said when he will choose his running mate.

Ehrlich also has not picked a replacement for Lt. Gov. Michael Steele, who is running for the U.S. Senate. Aides say they do not expect an announcement any time soon.