Montgomery County Democrats on Monday evening named Jheanelle Wilkins, senior field manager for the Leadership Conference on Civil and Human Rights, to fill a vacant House seat for Maryland’s District 20 (Silver ­Spring-Takoma Park).

Wilkins, 28, replaces former delegate William C. Smith Jr., who succeeded Jamie B. Raskin (D-Montgomery) in the state Senate after Raskin was elected to Congress this November. The contest was closer than the final tally suggested, the culmination of several weeks of intense behind-the-scenes courting of central committee members.

It took three rounds of balloting to winnow the field of six candidates down to Wilkins and Lorig Charkoudian, a professional mediator and criminal justice activist. Wilkins was selected by the county’s Democratic Central Committee by a vote of 19 to 9. She sits on the 28-member central committee and was able to vote for herself.

She received most of the party establishment’s support, including that of Gino Renne, president the United Food and Commercial Workers Union Local 400 (MCGEO), which represents about 5,000 nonuniform county employees, and Montgomery’s African American and Latino American Democratic clubs. In letters to the committee, tenant activists praised her advocacy for renter protection legislation passed last year by the Montgomery County Council.

Wade Henderson, the Leadership Conference president and chief executive, also writing to the committee, called Wilkins “a passionate and effective advocate for the rights of the most vulnerable in our society, including immigrants, the formerly incarcerated and children.”

Wilkins got a boost from committee concerns about a lack of diversity in the county’s 32-member Annapolis delegation. She becomes just the third African American woman to represent Montgomery in the General Assembly. The second, Morgan State University professor Pamela Queen, was selected by the panel in February to fill a vacancy in District 14. Karen Britto served eight months of an unexpired term in District 16 in 2010.

Charkoudian, 43, came to the race with a long history of community activism, including mediation and conflict resolution to help released prisoners reenter society. She is on the board of the Crossroads Community Food Network, which operates a farmers market and a community kitchen to help low-income people begin food businesses. She was endorsed by former delegate Heather Mizeur, who represented District 20 from 2007 to 2015.

The four other applicants were Daniel Koroma, outreach manager and liaison to African and Caribbean communities in the county’s Office of Community Partnerships; Darian Unger, a volunteer firefighter and Howard University School of Business professor; Yvette Butler, state director of the League of United Latin American Citizens; and Amy Cress, communications director for Easter Seals in the Washington area and an anti-gun-violence organizer.

“They were all excellent candidates,” said Tim Whitehouse, a central committee member who voted for Charkoudian.

Wilkins’s victory could add to debate about the state law that requires committee members to fill legislative vacancies by appointment rather than special election. Critics call it an undemocratic practice that can favor insiders.

Queen was a member of the committee, and Britto was its chairman, when each of them were named. Ten of the county’s 32 state lawmakers have gained seats in the House or advanced to the state Senate through party appointments. Whitehouse, who opposes appointments, said the panel “took some small steps” this time to bring more transparency to the selection, holding three large forums where the public could question candidates.

“They need to take some big steps in the next three or four years,” said Whitehouse, who supports a change in the law.

The committee vote is technically a recommendation to Gov. Larry Hogan, who makes the appointment. Hogan, a Republican, is required by law to appoint someone from the party that held the seat.