Her victory was the most high-profile upset on a night of sweeping change in Boston politics. Two members of the Massachusetts House leadership were defeated by political newcomers: Byron Rushing, a 28-year state representative, lost to Jon Santiago; and Jeffrey Sánchez, the House budget chief, lost to Nika Elugardo. In the Suffolk district attorney’s race, Rachael Rollins is poised to become the first woman of color to serve as Boston’s top prosecutor, topping a field that included a sitting prosecutor backed by the law enforcement establishment.

With no Republican in the race, Pressley, 44, is poised to become the first woman of color from Massachusetts to serve in the US House, in a storied district that, although reconfigured, was once represented by John F. Kennedy and the legendary speaker Thomas P. “Tip” O’Neill Jr.

The national wave of insurgent energy that is reshaping Democratic politics crashed into Massachusetts on Tuesday as Ayanna Pressley, the first African-American woman elected to the Boston City Council, made history again, defeating Representative Michael Capuano, a 10-term incumbent heavily backed by the political establishment.

Pressley’s victory over Capuano, a 66-year-old down-the-line liberal first elected to Congress in 1998, represents a generational, gender, and racial shift in Boston politics, and an upending of the wait-your-turn ethos that has pervaded the Democratic Party locally and statewide. With about 99 percent of precincts reporting, she had captured 59 percent of the vote to Capuano’s 41 percent.


Her success demonstrates the power of the party’s restive grass roots, which have buoyed a host of younger, nonwhite, and female candidates nationwide such as Andrew Gillum, the Democratic nominee for governor in Florida, Stacey Abrams, the Democratic nominee for governor in Georgia, and Alexandria Ocasio-Cortez, a 28-year-old political newcomer who won a New York congressional primary in June.

As soon as Pressley’s victory was announced at the electrical workers’ union hall in Dorchester, her supporters broke into tears and sobs. Challenging an incumbent, “I knew I would be demonized as entitled and what no one woman can ever be — ambitious. But change can’t wait,” she said, echoing her campaign slogan.


Capuano delivered a two-minute concession speech to his supporters at the Somerville Holiday Inn.

“I’m sorry it didn’t work out, but this is life, and this is OK,” he said. “America is going to be OK. Ayanna Pressley is going to be a good congresswoman and Massachusetts will be well served.”

For Pressley, the victory in the Seventh Congressional District opens a new chapter in a remarkable personal journey. She was raised in Chicago by her mother, Sandra, a community organizer, while her father, Martin, struggled with drug use and was incarcerated. She survived sexual assault as a child and then again as a student at Boston University, before going on to serve as an aide to Representative Joseph P. Kennedy II and Senator John F. Kerry.

In 2009, she broke racial barriers when she became the first black woman elected to the Boston City Council, a victory that announced her arrival as a rising star in the party. Her win on Tuesday signaled the falling of another barrier in Boston, a city with a painful racial history that still bears the scars of the busing crisis.

When she takes office in January, Pressley will represent the only congressional district in Massachusetts where a majority of residents are nonwhite.


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“It’s a new day,” said Alfreda Harris, a veteran African-American activist and former Boston School Committee member from Roxbury. “Younger people are getting involved in politics, and particularly black women. It’s good for the country and it’s good for the state of Massachusetts.”

In her race against Capuano, Pressley faced formidable opposition in a state known for entrenched politics that protects incumbents.

Capuano, drawing on his deep connections, marshaled support from the Massachusetts AFL-CIO, the building trades unions, and mayors across the district, including Martin J. Walsh of Boston, who activated his field operation to help the congressman push his supporters to the polls.

Capuano also raised nearly twice as much money as Pressley, and outspent her by a 2-to-1 margin, allowing him to advertise heavily on broadcast and cable television, while she was limited to a small ad buy on two Spanish-language stations.

Many prominent black leaders, including Representative John Lewis, a civil rights icon, and Deval Patrick, the state’s first black governor, snubbed Pressley and endorsed Capuano, calling him a friend and steadfast ally.

Pressley, however, mobilized a coalition of liberal, younger, and nonwhite voters by promising a new approach to the job.

While Pressley and Capuano agreed on most issues, she argued that it was “not a profile in courage” to have a progressive record in a deep-blue district. She vowed to bring “activist leadership” that reflected the take-it-to-the-streets mood of voters who are marching for gun control, immigrant rights, and women’s rights in the Trump era.


She also talked about issues that Capuano, a former Somerville mayor known for delivering federal funding to the district, has not made as prominent.

She promised to address violence against women, structural racism, and gun violence, as well as the wide racial and economic disparities in the district, which stretches from Randolph to Everett and includes the biotech offices of Kendall Square and the bodegas and barber shops of Roxbury.

Pressley hugged a supporter on election night. Craig F. Walker/Globe Staff

With her refrain that, “the people closest to the pain should be closest to the power,” she evoked the #MeToo movement as well as her own history as a survivor of sexual assault.

In June, after Ocasio-Cortez stunned the political world by defeating Representative Joe Crowley, another 10-term white incumbent, it gave Pressley a flood of national attention that cast her as the next gate-crasher to challenge the party establishment.

Still, the comparisons were, in some ways, overdrawn.

While Crowley was criticized for not living in New York and taking his race for granted — even skipping a debate with Ocasio-Cortez — Capuano took Pressley’s challenge seriously, debated her three times, and emphasized that he still lives in Somerville, near where he grew up.

He campaigned vigorously on his unwavering liberal record and staunch opposition to President Trump’s agenda. He argued that since he and Pressley agreed on most issues, his seniority and relationships in Congress would allow him to be more effective.

Still, there were few policy differences in the race. Pressley supported the growing movement to abolish Immigration and Customs Enforcement; Capuano argued the agency could be reformed.


She rejected corporate PAC money; he had accepted more than $700,000 from corporate political action committees since 2017, according to the Center for Responsive Politics.

Despite broad support from major political figures, Capuano was unable to secure endorsements from the state’s two US senators, Elizabeth Warren and Edward J. Markey, who remained publicly neutral. Attorney General Maura T. Healey backed Pressley.

Globe correspondent Amelia Nierenberg contributed to this report. Michael Levenson can be reached at mlevenson@globe.com. Follow him on Twitter @mlevenson.