A 10-term Democratic congressman has conceded defeat to a Boston city councillor who is now poised to become Massachusetts' first black congresswoman in a race with parallels to a NY upset that rattled the party in June.
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.
"It seems like change is on the way", Pressley said to cheers during her speech.
The 63-year-old Lynch is a former union ironworker and grew up in South Boston.
Pressley has always been identified as a rising star in the Democratic Party.
Capuano conceded to Pressley a little more than an hour after polls closed.
Capuano was the only Democratic incumbent in MA to lose a primary Tuesday night, with three others easily fending off challenges from the left.
In a video clip of the moment, her family and staff can be heard shrieking and crying in the background as Pressley begins to hug those around her.
Pressley represents the latest underdog candidate to have emerged to challenge both establishment Democrats and Republicans.
The prospect of a Pressley upset had drawn some comparisons to Alexandria Ocasio-Cortez's defeat of Crowley in June.
"With so much at stake in the era of Trump, tonight's results make clear what Ayanna Pressley knew when she boldly launched her campaign against a ten-term incumbent: Change in the country and Congress can't wait", said Jim Dean, chair of the liberal group Democracy for America. Parallels between Pressley and Ocasio-Cortez were quickly observed as Pressley went up against a Democratic incumbent who was first elected into office in 1998.
Pressley's win echoed that of Alexandria Ocasio-Cortez's over the long-time representative Joe Crowley in NY, and the ascent of Stacey Abrams in Georgia, who - if she wins - will become the first African-American female governor in U.S. history.
The Chicago-raised activist faces no Republican rival for the district, leaving her free to focus on President Donald Trump.
Two other Democratic House incumbents, William Keating and Joe Kennedy, fended off primary challenges on Tuesday.