A majority of the D.C. Council will be women for the first time in more than 20 years, and a majority will be Black for the first time since 2012, after voters chose a young mother who calls herself a “pragmatic progressive” from a field of 23 at-large hopefuls.

The ascension of Christina Henderson can be seen as a rebuke to left-wing activists, establishment Black moderate power and the rough politics of negative campaigning.

Henderson, 34, will join Brooke Pinto and Janeese Lewis George — who won Democratic primaries in June and easily secured victory Tuesday — as the newest members of the council. All three replace men on the panel.

“Women voters in D.C. decide elections,” Henderson said Wednesday. She campaigned on issues including child care and maternal health care, and ran a data-driven campaign that targeted female voters.

Two at-large seats were up for grabs, including one being vacated by outgoing member David Grosso (I), who endorsed Henderson, his former deputy chief of staff.

Incumbent Robert C. White Jr. (D) was the top vote-getter, while Henderson was well ahead of former council member Vincent B. Orange with some absentee ballots still to be counted.

Close behind Orange were Marcus Goodwin, a real estate developer, and Ed Lazere, whom labor unions and left-leaning activist groups worked to elect. All three conceded the race.

The electoral map shows a city cleaved in two, with Henderson bringing together voters in deeply disparate sections.

In mostly African American neighborhoods, Orange racked up votes, second only to incumbent White east of the Anacostia River. A former Ward 5 council member, Orange also won that district and was narrowly ahead of Henderson in Ward 4.

“I’m familiar with him. He’s been around a long time,” said Darlene Frederick, 70.

But in wealthier, Whiter neighborhoods, Orange barely registered, winning just 4 percent of the vote in Wards 2 and 3.

For Lazere, the reverse was true: He won strong support west of the river, especially in gentrifying Ward 1, but drew only 4 and 2 percent, respectively, in Wards 7 and 8.

Lazere and Henderson both labeled themselves “progressive” and shared liberal stances including raising taxes on the wealthy and dramatically expanding rent control. But Henderson staked out differences in tone and substance.

She said the city should keep its police force at the current size, while Lazere campaigned on reducing the police budget. While Lazere ran as unapologetically left-wing, Henderson preached an incremental strategy and willingness to compromise.

In a year focused on racial justice, many voters said they were interested in electing a Black woman.

“We see across the country, women lead differently,” Henderson said in an interview at her home in Petworth. “And so, as we are facing some particularly difficult challenges coming up, I think the tenor of the debate and type of debate and conversation we are having will be different.”

Lazere supporter Dyana Forester, the president of the AFL-CIO’s Metro Washington Council, said Lazere’s views on policing may have hurt him in Ward 7, where Forester lives, and in other Black neighborhoods. Voters there, especially senior citizens, are wary of rising crime and skeptical of Lazere’s defund-the-police approach, she said.

Forester also noted that Henderson and Orange were listed first and second on the ballot. Lazere was second-to-last, meaning voters with paper ballots had to keep reading the long list. Some who used electronic voting machines said they had trouble figuring out how to click down the list until they reached his name.

Henderson was endorsed by the editorial board of The Washington Post (which operates independently of news reporters), and by council member Mary M. Cheh (D), who represents high-turnout Ward 3.

The only major candidate who did not have name recognition from previous runs for office, Henderson juggled campaigning with her work in the office of Senate Minority Leader Charles E. Schumer (D-N.Y.) and with caring for her toddler daughter. Many voters said they were drawn to her knowledge of child care and educational needs in the District and because she is a Black woman.

“Her stance was a lot on child care and early childhood development,” said Regina Walgamott, who took her 5-month-old son, Wesley, in a stroller to put her ballot in a drop box at Eastern Market.

Beza Debru, a graduate student at George Washington University, called Lazere the choice of her head, with his lengthy record of activism, but Henderson the choice of her heart. “She’s young, up and coming. She’s also Black,” he said. “You just have to invest in people and see where they land.”

Political strategist China Dickerson said Henderson wisely seized on voters’ concerns about racial equity and directed her message well. “I have told almost every woman of color I know — if you ever have thought about running for office, now is the time to do it,” she said.

After calling to congratulate Henderson on Wednesday, Mayor Muriel E. Bowser (D) said at a news conference: “It looks like we’re going to have a majority female council in the District of Columbia. You won’t be surprised that makes me very happy.”

Many observers had characterized the race as a fight between moderates such as Orange and Goodwin, and the left-wing views of Lazere. Supporters of the three publicly sniped at each other, and the men traded barbs during forums. Henderson stayed out of it all.

“I can’t think of a single negative thing she did during the campaign,” said council member Charles Allen (D-Ward 6), who did not endorse a candidate.

Political strategist and Goodwin supporter Chuck Thies pointed in particular to an argument that arose when Lazere supporters from the environmentalist Sunrise Movement protested at the home of council member Anita Bonds (D-At Large). Goodwin called the protest inappropriate, while Lazere defended the right to demonstrate against elected officials.

“If [Lazere] ever had a shot, that ended it,” Thies said. “A beloved woman like Anita Bonds? It’s like yelling at your grandmother.”

Henderson, who won a respectable 9 percent in Ward 8, disputed the idea that Lazere was the primary candidate pushing a liberal agenda. “That was always the false narrative, that there was only one progressive that was running,” she said. “There were multiple of us on the ballot.”

Grosso, who is one of the most liberal members of the council, said his former aide may not be the reliable vote that activists wanted in Lazere. And that’s a good thing, he said.

“To any interest groups or unions — they put all their eggs in one basket because they knew where Ed was going to be on their issues. That’s comfortable, [but] it’s not the best thing for the city,” he said. “It’s important to look at every angle of a particular issue and then make a decision.”

He said he was delighted to be leaving his seat in Henderson’s hands.

“It’s important to see that sometimes a White man is willing to step back and make room for diversity,” he said. “I wasn’t going to step back and just allow anybody to take my seat. I wanted a really strong, qualified Black woman.”

Michael Brice-Saddler contributed to this report.