By Eric Bradner, CNN

Ayanna Pressley became the latest primary challenger to upset a sitting Democratic member of Congress on Tuesday, defeating Massachusetts Rep. Mike Capuano in the Boston-area district once represented by John F. Kennedy.

The 44-year-old Pressley -- who eight years ago became the first black woman ever elected to Boston's city council, and campaigned for a more activist style of leadership -- has long been seen as a rising star in Democratic politics.

She joins a growing group of younger, progressive Democrats -- often women and people of color -- to win competitive primaries, a week after Tallahassee Mayor Andrew Gillum, 39,became the first black person to win a major party's nomination for governor in Florida.

Pressley was seen as the next Alexandria Ocasio-Cortez-style giant-slayer who could take down an incumbent House Democrat. But there are major differences between the two candidates and their races: Ocasio-Cortez came out of nowhere to defeat New York Rep. Joe Crowley. Pressley, though, was already a well-known figure in Massachusetts politics, and the race was seen as close and competitive for months.

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The Massachusetts 7th District race was also not a moderate-vs.-progressive match-up.

Capuano, a 20-year incumbent, was one of the most progressive members of Congress. That made for unusual dynamics: The Congressional Black Caucus PAC had endorsed Capuano. But Pressley is now poised to become the first person of color Massachusetts has ever sent to Congress.

Pressley said the two would vote the same -- but that their styles would be different.

One of her go-to lines, said at a recent campaign event in Cambridge, was that "we might vote the same way but we will lead differently. These times require, and this district deserves bold, activist leadership."

She raised less money than Capuano and spent it on get-out-the-vote efforts, Spanish-language ads and other efforts to target young and minority voters.

One of their most significant differences was over the tactics of former NFL quarterback Colin Kaepernick. Pressley backed Kaepernick's decision to kneel during the National Anthem, while Capuano said the tactic "divided America."

Pressley has long been a Democratic star in the making who's been closely watched since her 2015 speech at an EMILY's List event headlined by Hillary Clinton -- but, with no members of Congress retiring, had no path to the national stage.

Pressley is a commanding stage presence who frequently ditches microphones; she doesn't need them.

Her campaign slogan -- "Change Can't Wait" -- connected the Democratic optimism of the early Barack Obama years to the urgency of Donald Trump's presidency.

In an effort to reach voters she says have been ignored, she talks openly about her father being incarcerated for much of her childhood and how she is a rape survivor.

Her go-to line, that "the people closest to the pain should be closest to the power," explains her calls for change in a district where people of color now outnumber white people.

In a recent interview at Tacos El Paso, a Mexican restaurant in Everett, she said she'd long idolized Shirley Chisholm and Barbara Jordan, pioneering Democrats who were among the first black women in Congress.

That she'd diversify Massachusetts' all-white, mostly male House delegation is "the bonus" of her candidacy she said during that interview.

"It's about who I listen to and it's about who I govern with. And there are a lot of people in this district who feel left out and left behind and ignored -- and it's not just women, it's not just people of color," Pressley said. "It runs the gamut. And I think after a generation, the district deserves a choice."

The 7th District is heavily Democratic, and Pressley is now expected to coast to victory in November.