Democrats in Florida picked liberal Tallahassee Mayor Andrew Gillum to run for Florida governor, while Democrat Stacey Abrams in Georgia is vying to become the first black woman to serve as governor of any USA state.
Pressley challenged Capuano, who has been in Congress since 1998, from the left, and the race drew comparisons to Alexandria Ocasio-Cortez's upset victory over Congressman Joe Crowley - particularly after Ocasio-Cortez endorsed Pressley.
In a video posted by her close friend Jesse Mermell, Pressley stands up in seeming disbelief.
Democratic candidate for U.S House of Representatives Ayanna Pressley's step-father Warren Maynard celebrates after Pressley won the Democratic primary in Boston, Massachusetts, U.S., September 4, 2018.
Pressley is the first woman of color ever to serve on Boston's City Council, and is set to break another barrier, becoming the first woman of color to serve in its congressional delegation.
When the 44-year-old rising star in the Democratic Party heard the results, she just couldn't believe it.
Ducey appoints Kyl to succeed McCain
Once Kyl is sworn in, Republicans will return to the 51 seats they held in the 100-member Senate before McCain's death . Joseph Lieberman, a former U.S. senator and close friend, said on CNN: "I say goodbye and my heart will be heavy".
There is no Republican challenger in the November general election.
It is the latest in a series of victories for progressive, young and minority candidates representing the opposition party.
However, two other Massachusetts Democrats, Reps.
Pressley will vie for a seat in the House of Representatives after a career in Boston's City Council. Joseph P. Kennedy II and former Sen.
Another veteran congressman, Democratic Rep. Richard Neal, won a spirited primary showdown with Tahirah Amatul-Wadud, a black attorney from Springfield who had hoped to become the first Muslim to serve in Congress from MA.
An African-American woman pulled off an upset victory in a Democratic primary contest against a 10-term entrenched male incumbent in Boston, the latest sign that insurgent USA candidates from the left are gaining ground.
However, unlike Crowley, Capuano had fiercely contested the MA race by racking up endorsements, attending debates and highlighting his consistently liberal voting record in one of the most Democratic districts in a traditionally Democratic state.