And unlike Ocasio-Cortez, a 28-year-old political neophyte, the 44-year-old Pressley has a track record in Massachusetts' halls of power.
Capuano is considered one of the most liberal members of the MA delegation, and Pressley had acknowledged she had few major policy quarrels with him.
"It seems like change is on the way", Pressley said in her celebratory speech.
The 7th District encompasses Boston's residential neighborhoods and its surrounding suburbs, with large Hispanic, black and Asian populations, and is the state's only majority-minority district. U.S. Rep. Joseph Kennedy, a grandson of former Attorney General Robert F. Kennedy, also endorsed the incumbent, calling him "a guy who won't shy away from steep odds or tough truths". Because of a Boston city election rule, Garrison's finish may be just enough to shimmy her way in to the council.
In nearby Connecticut, Jahana Hayes is on track to become that state's first black woman to win a congressional seat if she prevails in November. As FiveThirtyEight reports, a MA candidate has followed in the footsteps of the young Ocasio-Cortez with a surprising upset against a mainstream Democrat challenger on Tuesday evening.
Polls and political analysts predict the state's nine House of Representatives seats will remain in Democratic hands, along with the seat held by US Senator Elizabeth Warren, often cited as a possible 2020 White House contender.
MA senator Elizabeth Warren, a favourite to run in the 2020 Presidential election, was uncontested for the state's Democratic nomination. Neal, the dean of the state's House delegation, first was elected in 1989.
Another 10-term incumbent went down to defeat in a Democratic primary Tuesday night. Baker will face Democrat Jay Gonzalez in November.
Capuano also had the backing of the Congressional Black Caucus PAC, and Massachusetts's first African-American governor, Deval Patrick.
"At a time when our country is having trouble finding common ground on so many issues, we in MA are the exception", Baker told supporters. Both contended that Baker's support among voters was soft and that his administration had failed to make significant strides in many areas, particularly the problems plaguing the Boston-area transit system known as the "T".