On Tuesday Senator Ed Markeysuccessfully fended off a challenge from RepresentativeKennedy III in the Massachusetts Senate primary after facing what was initially seen as an uphill climb against a rising Democratic star and member of the most famous political family in the U.S.

The senator himself addressed his supporters during his victory speech on Tuesday, calling his win a “reaffirmation” of the progressive movement.

“Tonight is more than just a celebration of a movement,” Markey said, speaking from his hometown of Malden, Mass. “It is a real reaffirmation of the need to have a movement, a progressive movement of young people demanding radical change, demanding justice.”

The incumbent senator’s victory comes nearly a year after Kennedy, 39, entered the race with a double-digit lead over the 74-year-old incumbent senator, drawing media attention from Massachusetts and beyond.

A Change Research survey conducted in August 2019 before Kennedy announced his candidacy showed the congressman with a whopping 17-point lead over Markey.

But polls in recent weeks signaled the tables had turned, with Markey leading his opponent by double digits in some cases. Now, Kennedy has become the first member of his family to lose a statewide race in Massachusetts.

“If you’re a Democrat in Massachusetts, you’re frequently confronted with a surplus of talent,” Walsh said. “In primaries, we are lots of time choosing not between good and bad; we’re choosing between good and better. And in this case, Joe Kennedy is damn good, but Ed Markey is better.”

It marks a stunning change in fortune for Kennedy, who has been seen as a likely future presidential contender and garnered national attention in 2018 when he delivered the rebuttal to President Trump’s State of the Union address.

Like Markey, Kennedy had liberal bona fides, having served on the House Progressive Caucus and been vocal in the fight for racial justice, notably spending time and advocating for the family of DJ Henry, an unarmed Black man originally from Massachusetts who was killed by police a decade ago.

Additionally, his last name made him a popular commodity in Massachusetts. Two of Kennedy’s great uncles, the late President Kennedy and the late Sen. Edward Kennedy, both served as Democratic Massachusetts senators. Joe Kennedy’s grandfather Robert F. Kennedy served as a Democratic New York senator.

But Markey benefited from widespread support from major progressive groups ranging from the Sunrise Movement to MoveOn to Our Revolution. He also garnered the backing of progressive leaders such as Representative Alexandria Ocasio-Cortez, fellow Massachusetts Senator Elizabeth Warren and activist AdyBarkan.

Progressives celebrated Markey’s win on Tuesday, adding it to the list of primary wins this summer.

“Before tonight, a Kennedy had never lost an election in Massachusetts. But even a 100 year dynasty can not overcome the Green New Deal,” the Sunrise Movement tweeted.

Progressives were particularly favorable of Markey’s work on climate change issues, including his co-authorship of the Green New Deal with Ocasio-Cortez. Recent polling shows the legislation is popular with Massachusetts Democrats.

A Data for Progress poll released last month showed 83 percent of the state’s Democratic primary voters said they backed the Green New Deal, with 58 percent saying they strongly supported it and 25 percent saying they somewhat supported it.

“Ed Markey didn’t just support the Green New Deal — he ran on it, making his leadership on climate front and center in his case to voters,” wrote Evan Weber, the political director of the Sunrise Movement, in a memo.

“Though none of us were thrilled to have to direct so much energy to a major primary fight in blue Massachusetts that would likely peak in the fall of 2020, Sunrise and the Markey campaign collectively committed to using the campaign as an opportunity to grow the power of the movement for a Green New Deal both nationally and in Massachusetts,” Weber wrote.

The group, which is youth-led and advocates for combating climate change, endorsed Markey a month before Kennedy jumped into the primary. Weber wrote that the group’s presence in Massachusetts grew from 18 local hubs to 45 city, town, high school and college hubs across the commonwealth.

Sunrise’s support for Markey spanned from a local, grassroots level to a nationwide level. Weber said the Sunrise Lexington Hub, a local hub mostly made up of high school students, held 14 of its own phone banks. At the national level, the group predicted it would have made more than 200,000 nationally coordinated calls for Markey by the time polls closed on Sep. 1.

Additionally, progressives appeared successful in flipping the script by portraying incumbent Markey as the insurgent in the race and painting Kennedy as an establishment figure.

Kennedy got a major last-minute boost when House Speaker Nancy Pelosi made the rare move of wading into a Senate primary, throwing her support behind Kennedy. She cited loyalty to her own members as part of her decision, though a number of progressives called the move hypocritical due to the resistance their primaries against incumbents have received from the Democratic establishment.

“A lot of times we are running insurgent campaigns to replace Democrats who don’t deliver on values and a progressive agenda, and sometimes we gotta protect our own,” said Our Revolution field organization Mike Oles on a call with Markey and supporters last week. “You are being challenged from the right,” he added.

Progressives also highlighted Kennedy’s status as a member of the country’s most prominent political dynasty, something Kennedy did not mention for the majority of the campaign.

“We’re going to be with you every minute,” Oles said on the call with Markey. “Obviously the Kennedy name is big, but the grassroots progressive movement is bigger.”

The fact that Kennedy also supported many of the progressive causes backed by Markey meant he needed to come up with a satisfying explanation as to why he was challenging the sitting senator, something critics say he failed to do.

“I believe that Massachusetts should be getting everything they possibly can out of our senator, and I don’t think we’re getting it,” Kennedy told The Hill last week, arguing Markey was not present enough in the state during his tenure in the Senate.

But Markey and his supporters, including Ocasio-Cortez, argue that the senator was the original champion of the ideas, which they say ultimately matters most to voters.

“When she said, ‘It’s not your age but the age of your ideas,’ when she said that Ed Markey was the generational change that we have been waiting for, it helped to make clear that in this race I am the youngest guy because it’s about ideas,” Markey told The New York Times this week.