Sarah Elfreth, the youngest woman ever elected to Maryland’s State Senate, won a crowded Democratic primary race on Tuesday in Maryland’s Third Congressional District, according to The Associated Press.

Ms. Elfreth, 35, emerged from a field of more than 20 Democrats vying in the deep-blue district to succeed Representative John Sarbanes, a Democrat who announced last October that after nine terms he would not seek re-election.

First elected to the Maryland State Senate in 2018, Ms. Elfreth often highlighted her political résumé during her run and played up the bipartisan legislative victories she helped to secure while serving in the General Assembly. She ran on a platform with standard Democratic fare that included pledges to protect abortion rights, combat gun violence and fight climate change.

Ms. Elfreth drew support from several local Democrats. Senator Ben Cardin of Maryland, who did not seek re-election this year, spoke favorably of her while appearing on the trail alongside her last week — though he stopped short of a formal endorsement.

Her most prominent rival was Harry Dunn, a former Capitol Police officer who was on duty during the attacks on Jan. 6, 2021, and rose to national fame after testifying in the House investigation into the attack. Mr. Dunn, a first-time candidate, had significantly out-raised his opponents in the race since announcing his run in January, and was endorsed by a number of prominent national Democrats.

Ms. Elfreth had raised about $1.5 million since starting her campaign in November, significantly less than the $4.6 million that Mr. Dunn had amassed. But she received support from outside groups, including more than $4.2 million in spending from the United Democracy Project, a super PAC affiliated with the American Israel Public Affairs Committee, the pro-Israel group.

Her support drew attacks from Mr. Dunn, who swore off funding from outside groups and criticized Ms. Elfreth for at times voting alongside Republicans in the State Senate. Ms. Elfreth, for her part, said she would prioritize campaign finance reform in Congress, and her campaign accused Mr. Dunn of distorting Ms. Elfreth’s record.

Ms. Elfreth will be favored in the heavily Democratic district in November.