Massachusetts Sen. Ed Markey is seen here speaking at a news conference to unveil the Green New Deal in February 2019.

Alex Wong/Getty Images

hide caption

toggle caption

Alex Wong/Getty Images

Massachusetts Sen. Ed Markey is seen here speaking at a news conference to unveil the Green New Deal in February 2019.

Alex Wong/Getty Images

Massachusetts Sen. Ed Markey has fended off the highest-profile Democratic primary challenge of his decades in federal office, defeating the rising Rep. Joe Kennedy III, a member of the state’s legendary political dynasty.

Kennedy conceded the contest nearly two and a half hours after polls closed Tuesday night. The Associated Press projected Markey as the winner a short time later. Prior to this race, no member of the Kennedy family had lost an election in Massachusetts, according to the Cook Political Report.

Markey’s victory means the 74-year-old incumbent, who became a Massachusetts congressman before the 39-year-old Kennedy was born, advances to November’s general election and will likely continue to represent the solidly liberal state in the Senate for another six years, while Kennedy — at least for a time — will be out of Congress, since state law prohibited him from running for reelection to his House seat and in the Senate primary at the same time.

The outcome adds a new twist to an emerging narrative in Democratic politics. Over the last two years, young progressive challengers have toppled well-known longtime incumbents in places like St. Louis and New York City. In the Massachusetts race, though, it was Markey who received support from progressive figures and organizations for his reelection, and his challenger, Kennedy, whose famous surname boosted his name recognition.

Indeed, before Kennedy even entered the race, polling found him to be the favorite — and some analysts were counting Markey out.

Massachusetts U.S. Rep. Joe Kennedy III speaks during a congressional hearing on May 14.

Greg Nash/Pool/Getty Images

hide caption

toggle caption

Greg Nash/Pool/Getty Images

Massachusetts U.S. Rep. Joe Kennedy III speaks during a congressional hearing on May 14.

Greg Nash/Pool/Getty Images

But Kennedy’s bold challenge of the incumbent rubbed many voters the wrong way, and some Democrats, including former Massachusetts Rep. Barney Frank, bemoaned the fact that the primary would take resources and focus away from the party’s efforts to topple Republicans in races elsewhere. During the campaign, Kennedy was often asked to explain why he was taking on Markey, since the two agree on most major policy issues. Kennedy would say it was time for new leadership, and that being one of the state’s senators means more than just how that politician votes.

“For most who are struggling and scraping and striving across our commonwealth, the status quo doesn’t come close [to helping them],” Kennedy said this past weekend, according to WBUR. “And we will not change that by doing the same thing we’ve been doing for 50 years: by entrusting our future to the same people who built our past.”

Markey stressed his working-class roots, legislative accomplishments and progressive credentials, especially on climate change with his co-authorship of the Green New Deal with New York Rep. Alexandria Ocasio-Cortez, who endorsed him. (Kennedy also supports the Green New Deal.)

“Alexandria Ocasio-Cortez is right when she says, ‘It’s not a question of your age; it’s the age of your ideas,’ ” Markey told reporters this past weekend. “If [this campaign is about] ideas, I’m the youngest guy in this race.”

Kennedy, a former Peace Corps volunteer who speaks Spanish fluently, tried to counter by pointing to Markey’s vote to authorize the Iraq war and his record on criminal justice, including his vote for the 1994 crime bill — positions now out of step with the party’s progressives.

Markey was backed by his progressive colleague, Sen. Elizabeth Warren, and his campaign’s quirky digital presence boosted his appeal with young people. (Team Kennedy complained of online harassment from some Markey supporters.)

Markey reportedly outspent Kennedy nearly four to one on ads in the Boston market in the final week of the campaign.

The incumbent topped the final several polls in the race, led by support among young voters, white residents and college-educated liberals. Kennedy, meanwhile, polled stronger among moderates, nonwhite voters and voters without a college degree.

Markey now faces Kevin O’Connor, the winner of the Republican primary, in November.

Another longtime Massachusetts incumbent, 1st Congressional District Rep. Richard Neal, also fended off a younger challenger on Tuesday.