SPRINGFIELD, Mass. — Democratic Rep. Seth Moulton began clamoring for generational change long before it became a political cliche.

The Iraq War veteran and Harvard graduate won his North Shore congressional seat in 2014, after dislodging a nine-term Democratic incumbent. A few years later, he led an ultimately unsuccessful uprising against Nancy Pelosi, then the party’s most powerful woman. And a year after that, he took a stab at running for president; his long-shot bid lasted all of four months.

Now, at 47, Moulton is making another bold gambit. He’s taking on Sen. Edward J. Markey, a steadfast progressive who’s been a fixture in Massachusetts politics for longer than Moulton has been alive. 

In the final stretch before Tuesday’s Democratic primary, Moulton is crisscrossing the state in a quest for votes. Polls suggest it’s an uphill climb: A University of New Hampshire survey released Wednesday found Markey with a 35-point lead.

Moulton is undaunted. He points to recent polling misfires in Wisconsin and Michigan, and is counting on broad dissatisfaction with the status quo to lift him to victory.

“I’m running against an 80-year-old senator who I respect,” Moulton told a voter here last week at a cookout hosted by the local sheriff that drew about 3,000 people from across Western Massachusetts. “But it’s time for a new generation of leadership to take on a new generation of challenges and opportunities.”

The call for change that has reverberated through Moulton’s career is having a moment right now, with voters across the political spectrum voicing frustration at Washington’s gerontocracy. The lengthy and largely unexplained absence of former Senate Republican leader Mitch McConnell and the deaths of six older lawmakers over the past 18 months has only heightened the concern.

The push against entrenched incumbents is particularly pronounced in the Democratic Party, which is still grappling with the implosion of Joe Biden’s 2024 reelection campaign. Seven House Democrats have lost to primary challengers so far this year. 

But much of the insurgent energy is coming from the party’s left flank, and the Moulton-Markey match up doesn’t fold neatly into that narrative. 

Moulton maintains that “there are two progressives in this race,” but Markey disagrees. He points to the relatively moderate record Moulton has compiled over nearly six terms in the House, as well as his comments regarding transgender athletes. (Following the 2024 election, Moulton told The New York Times that he didn’t want his daughters “getting run over on a playing field by a male or formerly male athlete,” remarks he has since apologized for.)

Moulton’s efforts to recalibrate his image by stressing his progressive stances are a product of his political ambitions, not a shift in his core beliefs, Markey’s supporters say. 

“I am the progressive candidate,’’ Markey asserted in an interview Wednesday on MS NOW. “That’s why Bernie Sanders, that’s why Elizabeth Warren, that’s why Alexandria Ocasio-Cortez has endorsed me in this race.” Underscoring the point, Markey will host a rally Saturday with Sanders, Warren and Massachusetts Rep. Ayanna S. Pressley in Dorchester. 

Should he win reelection, Markey would be 86 at the end of his next term. He’s already said this is his last race. But he said, with Donald Trump in the White House, the stakes were too important for him to step aside now.

Markey grew up in Malden, which was then a blue-collar Boston suburb, and put himself through Boston College by driving an ice cream truck. He was first elected to the Massachusetts legislature when Richard M. Nixon served in the White House, then came to the House in 1976 and moved to the Senate after winning a special election in 2013.

“This is an extremely successful, extremely connected politician,’’ Tatishe M. Nteta, a political science professor at the University of Massachusetts Amherst, said of Markey. “People know that he’s old, that’s not a surprise. So Moulton has to do more than say, ‘This is an old man.”’

‘A lot of moonbats’

Matt L. Barron, a former congressional staffer and political strategist from Western Massachusetts, is backing Moulton but said the challenger hasn’t quite made the case to voters about why a switch in senators is warranted.

“There are a lot of moonbats in this state, that’s what left-wing Massachusetts Democrats are called, and they’re sort of programmed to go for Markey,’’ Barron said. “And if you’re the challenger, your job is to tell the voters why they should fire the incumbent and hire you and to do that you’ve really got to lay it out.”

“The age thing,’’ Barron added, “is appetizer. It’s not the main course.”

For some Massachusetts voters, though, Moulton’s core argument is a compelling one.

“A lot of these guys, they get in office and the only way you get them out is if they get really ill and have to leave, or they die,’’ observed Robert Haygood, a Democrat from Amherst, as he sat at a picnic table during the Springfield cookout. 

Haygood, 60, works for the state judicial system and noted that state judges in Massachusetts are required to retire at 70. “There should be the same rule in politics, 70 or 75 should be the cutoff,” he said. “After that, you’ve got to retire and let the new come in.”

At a recent debate, Markey was asked whether he used artificial intelligence. “I use whatever is inside my iPhone or my iPad, whatever comes up,” he responded.

To Moulton, Markey’s halting answer signifies the senator’s failure to grasp an essential technology reshaping American society, and it was quickly repurposed for a digital ad.

But Markey has weathered the age argument before: Democratic Rep. Joseph P. Kennedy III also made a case for generational change when he took on Markey six years ago. Kennedy wound up losing the primary by more than 10 points.

“Ed Markey knows no age,” said Arthur Powell, a member of the Democratic State Committee and a Markey supporter who lives in Moulton’s congressional district. “Joe Kennedy couldn’t beat him, and he’s a Kennedy and a super guy.”

To Moulton, age is shorthand for much of what ails the Democratic Party. He told the audience at a forum in Springfield last week that “Washington is broken” and that he’s running against a political establishment that has failed to deliver, reiterating his pledge not to support New York’s Charles E. Schumer as Senate majority leader if he’s elected and Democrats win control of the chamber.

Moulton has highlighted his legislative record, including his focus on improving mental health services, and his pushback against the Trump administration. And he’s pitched his plans for high-speed rail service and expanding affordable housing. 

In the waning days of the campaign, Moulton received the endorsement of The Boston Globe’s editorial board and brought New Jersey Gov. Mikie Sherrill, a former House colleague, to Massachusetts. (The two share a military background, and Moulton’s Save America PAC provided her political career with an important early boost.)

Outside groups have flooded the race with ads and mailers, with outfits supporting Moulton targeting independent voters, who can participate in party primaries in Massachusetts.

But with time running out, Moulton needs to do more than call his opponent old, said Nteta, the UMass professor, especially when “his long tenure in Congress is viewed as a positive.” 

“It’s a tall order to try to beat someone who has been in Massachusetts politics this long,” Nteta added, “and whose approval rating with the Democratic electorate is 82 percent.”