Ayanna Pressley just keeps checking off the “firsts.” In a stunning upset on Tuesday, the first woman of color to be elected to the Boston City Council took the Massachusetts 7th Congressional seat away from the 66-year-old Democratic incumbent, Michael Capuano, by 18 percentage points to become the first person of color to represent Massachusetts in the US House of Representatives.

With no Republican on the November ballot, Pressley is looking ahead to a smooth sail into office after an existentially bruising campaign. She won it, the 44-year-old Dorchester resident said, by letting the district’s unseen constituents be “foot soldiers in this movement.”

Defined by the campaign slogan “Change Can’t Wait,” Pressley presented her case as that of a daughter of a single mother and a father who was in and out of prison, a survivor of sexual assault, and a representative of communities that have always been asked to let the system slowly right itself. Pressley was convinced that the state’s only majority-minority district could do more to advance its causes.

“We have, together, ushered in something incredible,” she told ecstatic supporters on Tuesday night, flanked by her husband Conan Harris and stepdaughter Cora. “People who feel seen and heard for the first time in their lives, a stakehold in their democracy, and a promise for our future. That is the real victory that is bigger than any electoral victory.”

Capuano conceded defeat in remarks made to supporters at a Somerville hotel around 9:10 p.m. “We’ve done everything we could do to get this thing done,” he said. “Today was no exception .... I’m sorry it didn’t work out, but this is life. This is okay. America is going to be okay. Ayanna Pressley is going to be a good congresswoman. And I will tell you that Massachusetts will be well served.”

Pressley swamped her foe across a district that includes sections of Boston, Cambridge, Milton, Chelsea, Everett, Randolph, and Somerville by 59 to 41 percent. In a speech to a raucous audience at Dorchester’s IBEW Hall, Pressley praised her family, her supporters, and her opponent.
“Tonight is but the first step, but we have many more to take,” Pressley said. “Are you ready to come to Congress with me? Are you ready to bring change to Washington? Because... change can’t wait.”

For the progressive congressman, she had kind words. “Mike Capuano is unapologetically himself,” she said. In their meetings over the years, sharing a stage or sharing a bullhorn, she said, “He forced me to bring my best just like he did in this race and I thank him for his 20 years of service.”

Pressley added that she knew this would be a drawn out and trying race from the beginning.

“Ours was truly a people-powered, grassroots campaign launched just 195 days ago that dared to do what Massachusetts Democrats aren’t supposed to do,” Pressley said, referring to what she said was a difficult decision to challenge an incumbent. She added, “I knew we would be essentially alone, I knew we would find no favor with the Democratic establishment both here at home and in Washington and I knew we would have to fight for every dollar, every volunteer, every door, every voter. I knew I would be demonized as entitled and what no woman can ever be – ambitious. But change can’t wait.”

First elected to the City Council in 2009, Pressley formally announced her campaign for Congress last January. Off the jump, she stared down sitting politicians, commentators, and voters who could not see past the issues she shared with the veteran incumbent.

Capuano boasted endorsements from the likes of Mayor Martin Walsh, former Gov. Deval Patrick, US Rep. Joe Kennedy III, who supported him for the district once held by a young JFK, and was bolstered by a hefty advantage in campaign funds. Pressley, endorsed by both the Boston Globe and the Boston Herald, had other councillors and Attorney General Maura Healey at her back.

With little daylight between the two on current legislation – although they did split over her desire to defund ICE, with the councillor pledging to go further in advocating for women’s rights – Pressley pushed her case for diversity as a catalyst for fresh policy informed by grassroots voters and the constituents she would represent by citing her advocacy for liquor license reform and better supports for women and girls of color.

Her message clearly resonated with voters. In Boston, where she has thrice topped the ticket in competitive at-large council races, she pulled in an overwhelming 64 percent of the vote, her 17,000 vote Boston margin offsetting virtually every ballot the congressman pulled in from outside the city.

John Pham, 23, was among the last voters to squeak in under the wire at polling location Ward 15-4 on Bowdoin Street. Pressley dominated that precinct by 223 votes to Capuano’s 103. “I voted for Ayanna,” Pham said two minutes before the poll closed. His shift ran late, but he still booked it to cast his ballot for his fellow Dorchester resident. “I just felt like people who are from the neighborhood that I’m from would probably be more willing to help out the places where I’m from as well,” he said.

That pattern held across the city. While her home precinct in Ashmont, 16-8, was a squeaker where Capuano edged her out by 51 to 49 percent, Pressley was dominant across most of Boston, taking swatches of precincts by 70 and 80 percent. In Codman Square’s busy precinct 17-5, she pulled in 91 percent of the vote.

As she spoke to residents over the summer, Pressley saw that “the people in the Seventh expected more from their leaders” and having Democrats in office isn’t enough. “It matters who those Democrats are,” she said.