Sen. Edward J. Markey triumphed in the toughest fight of his near 44-year Capitol Hill career Tuesday, making Rep. Joseph P. Kennedy III the first member of the Kennedy dynasty to lose a Massachusetts election.

Markey, 74, won the Democratic Senate primary by rallying progressive Democrats to his cause and contrasting his own working-class roots with those of an opponent whose namesake and great-grandfather, Joseph P. Kennedy Sr., groomed his son John F. Kennedy to be president and sons Edward M. and Robert F. — the 39-year-old candidate’s grandfather — to be senators. 

Markey, who trailed by double digits in early polls, was leading Kennedy 55 percent to 45 percent when The Associated Press called the race at 10:30 p.m. Eastern time.

“Tonight is more than just a celebration of a movement, it is a reaffirmation of the need to have a progressive movement of young people demanding radical change,” Markey said in his victory speech Tuesday night. “Today is just the beginning.”

Prominent endorsements from liberal stars such as New York Rep. Alexandria Ocasio-Cortez and fellow Massachusetts Sen. Elizabeth Warren helped fuel Markey’s comeback — and his fundraising — as he portrayed himself as the true progressive in the race. Markey, whose father was a milkman and union member, also took aim at Kennedy’s patrician lineage. 

“We asked what we could do for our country. We went out, we did it,” Markey said in a stirring campaign ad, evoking the famous quote of President John F. Kennedy, his challenger’s great-uncle. “With all due respect,” Markey continued, arms crossed, looking into the camera, “It’s time to start asking what your country can do for you.”

Though it initially seemed that Kennedy, currently in his fourth term representing the state’s 4th District, would end Markey’s long legislative career, Markey seized on the challenge as an opportunity to brand himself as both a policy deal-maker and a progressive, especially on environmental and technology matters. 

Even a last-ditch endorsement of Kennedy by Speaker Nancy Pelosi didn’t slow Markey’s late-summer momentum.  

“When Joe Kennedy got in the race, there was a lot of excitement,” said Democrat Brad Bannon, a Massachusetts native and president of the polling and consulting firm Bannon Communications Research, who did not work on the race. “Markey has been an incumbent who didn’t keep the home fires warm, and so Joe Kennedy started out with a big lead. The excitement over the Kennedy name opened the door for him, but Joe never made the sale. He never made a compelling case about why Markey should be replaced.”

Failure to launch

The successful formula for some of the notable primary contests among Democrats this cycle and in 2018 has featured challengers who are both younger and viewed as more progressive than the incumbents. Examples include Ocasio-Cortez’s upset of New York Rep. Joseph Crowley and Massachusetts Rep. Ayanna S. Pressley’s victory over Rep. Michael E. Capuano, both in 2018. Earlier this year, the pattern was repeated when Jamaal Bowman defeated Rep. Eliot L. Engel in New York’s 16th District.

Kennedy had youth on his side, but even though he and Markey have similar voting records, Markey rallied progressive members and groups to his side, defusing what many Massachusetts political observers believed was an insurmountable challenge. 

Markey “was written off by a lot of the political establishment when Kennedy entered the race,” said Peter Ubertaccio, a political science professor at Stonehill College in Easton, Massachusetts. Instead, the longtime lawmaker recast his image.

“Now, he’s the center of attention in Massachusetts politics,” Ubertaccio added. “This could be an unusual moment for Markey.”

He ran on his sponsorship of Ocasio-Cortez’ Green New Deal legislation, aimed at combating climate change. It’s a controversial bill that even many Democrats don’t support, but in deep-blue Massachusetts, it’s no liability. Ocasio-Cortez cut an ad in support of him. 

Voting records in step

Little in the way of policy differences existed between Markey and Kennedy, who leads the Congressional LGBT Caucus’ Transgender Equality Task Force and, like the senator, supports “Medicare for All.” 

Markey has voted 99.5 percent of the time with his party on votes that split Democrats and Republicans since 2017, while Kennedy voted with his House colleagues 98.4 percent of the time over the same period, according to a CQ Roll Call analysis of their voting records.

When it comes to support for President Donald Trump’s agenda, they’re similarly in line against the commander in chief’s wishes. Markey voted for Trump’s preferred outcome in Senate votes 15.6 percent of the time since 2017, while Kennedy gave the ‘aye’ to the president’s preferred outcome in House votes just 9.7 percent of the time since 2017. 

“It’s really interesting how this race turned into somewhat of an ideological race,” said David Hopkins, a political science professor at Boston College, who writes the politics blog Honest Graft. “It wasn’t at all clear in the beginning when Joe Kennedy announced his challenge to Markey that there would be an ideological dimension to it. It seemed much more generational.  … One of the things that really struck me was Markey’s ability to leverage his Green New Deal sponsorship and AOC endorsement into a new persona for him as an outspoken progressive.”

Even though Markey and Kennedy swore off donations from corporate PACs last year, both raised huge piles of cash, and the race attracted more than $6.5 million from outside sources, including super PACs such as the Kennedy-supporting New Leadership PAC and the pro-Markey United for Massachusetts. 

Also on Tuesday, Massachusetts Republicans picked lawyer Kevin O’Connor as their nominee to challenge Markey in November. O’Connor was leading scientist and entrepreneur Shiva Ayyadurai 59 percent to 41 percent when the AP called the race at 9:49 p.m. Eastern time.

For Markey, however, the real battle was the primary and he appears to be a shoo-in for reelection in a race Inside Elections with Nathan L. Gonzales rates Solid Democratic. 

Markey grew up in Malden, a working-class suburb of Boston, and graduated from Malden Catholic High School and went on to Boston College where he earned bachelor’s and law degrees. He first entered the House in 1976 after winning a special election. In 2013, he moved to the Senate after winning a special election to replace Democrat John Kerry, who resigned to become secretary of State.

Kennedy, who also grew up in the Boston area, went to college at Stanford and law school at Harvard. He first won his congressional seat in 2012, succeeding longtime Democratic Rep. Barney Frank. 

In abandoning his House seat for the Senate attempt, Kennedy will be out of a job at the end of this Congress, fueling speculation about his future. Might he join a Biden administration should the Democratic presidential nominee prevail in November? Or seek elective office again? Kennedy hasn’t offered any clues yet.