Capuano was the only Democratic incumbent in MA to lose a primary Tuesday night, with three others easily fending off challenges from the left.
Pressley is now poised to become the only black member of Massachusetts' mostly male congressional delegation.
A 10-term incumbent congressman in MA conceded to a progressive candidate during the state's Democratic primaries Tuesday night. Her win comes at the tail end of a primary season in which black politicians have made a series of advances. Bernie Sanders (D-Vt.), she later supported it. Capuano also backed Sanders' quixotic health care scheme, which would cost approximately $32.6 trillion, according to Mercatus scholar Charles Blahous.
If recent upset victories for left-wing candidates in New York, Florida, Pennsylvania, and now MA are any evidence, this movement to oust the old guard of the Democratic Party and usher in young, ambitious progressives willing to challenge the traditional boundaries of American politics is rapidly gaining steam.
"This is a fight for the soul of our party". She congratulated Pressley, whom she referred to as her "sister in service", on the historic win Tuesday night. Capuano - along with the entire MA congressional delegation - supports the "Blue Lives Matter" bill, making assaulting a police officer a federal crime.More news: Rafael Nadal reacts to marathon match win with pure class
She'd argued on the campaign trail that systemic inequalities had worsened in a district that was once represented by John F. Kennedy and where the majority of voters are nonwhite.
Capuano is only the second Democrat to lose a primary this midterm season, the first was New York Rep. Joe Crowley, who lost to Alexandria Ocasio-Cortez.
Capuano said in his concession speech that "clearly the district wanted a lot of change". Baker will face Democrat Jay Gonzalez in November. Ocasio-Cortez worked the late Sen.
During the campaign, Capuano touted his credentials as an "unabashed liberal", but he found himself competing with Pressley over who was the more progressive candidate.
The race drew national attention because it was seen by some as a possible indication of deeper generational and philosophical shifts within the Democratic Party, led by younger candidates who take more liberal positions on issues ranging from universal health care to immigration enforcement.
Secretary of State William Galvin, the longest-serving constitutional officer in state history, held off his strongest Democratic primary challenge in years from Boston City Councilor Josh Zakim.