Stephen Lynch

For Lynch, 71, a contested primary is not new. But challenger Patrick Roath, a 39-year-old attorney and former Deval Patrick aide, is trying to exploit a restive Democratic base anxious for fresh voices in Washington, accusing the more moderate Lynch of clinging to “politics of the past” and energizing voters in ways his progressive predecessors hadn’t — despite many not knowing his name even a year ago.

Lynch has at times responded publicly with a metaphorical yawn. He has held relatively few formal campaign events beyond door-knocking, official appearances, and supporters waving signs on his behalf. The incumbent has largely ignored Roath’s demand for more debates and has dismissed Roath, who lives in Jamaica Plain, as a transplant because he grew up in Connecticut.

Still, his campaign on Thursday reported spending nearly $700,000 since the start of July, most of it on advertising — including a recent spot that features him jogging — and drawing down his campaign account by more than half.

Additionally, a dozen local Democratic town committee leaders told the Globe they sense Lynch is struggling to adapt to changing demographics in his South Shore-anchored district, pointing to an influx of younger, more liberal voters, or to reconcile his past positions, such as his opposition to the Affordable Care Act 16 years ago, that are at odds with the party’s increasingly liberal views.

Some said they also want a representative who can bring the “fight, fight, fight” attitude against President Trump they feel has been lacking in the party.

“Folks are feeling the vibe nationally within the Democratic Party. ... There’s a lot of progressive excitement,” said Meghan Haggerty, chair of the Milton Democratic Town Committee, who hasn’t endorsed a candidate. But she also is not blind to the dynamics here: Incumbents are hard to unseat.

“A lot of people know Congressman Lynch,” Haggerty said. “It seems competitive, and I think it’s a toss-up right now.”

Lynch, for his part, has been dismissive of his challenger’s odds, telling the Globe he had staved off previous progressive challengers with “more money and more of a buzz around them.”

In 2020, for instance, Lynch topped Robbie Goldstein, now the state’s public health commissioner, outrunning him by more than 30 percentage points. He also easily beat two primary challengers in 2018.

Neither Roath nor any of those candidates, Lynch said, had his experience over 12-plus terms in Congress.

In an hour-long forum last week in Weymouth, Lynch cited his position as the ranking Democrat on a subcommittee on artificial intelligence, his work securing affordable housing and hospital funding for the district, and his labor support as a former iron worker.

The experience-versus-new-blood argument, Lynch told the Globe, is a “perennial choice,” one he himself used when he first ran for Congress a quarter-century ago, winning a special Democratic primary on Sept. 11, 2001.

In a sign of how that’s changed, Lynch quoted “one of my predecessors, John Adams” — who served as a delegate for Massachusetts in the First Continental Congress — in his closing remarks last Thursday, saying, “Facts are stubborn things.”

“We’ve got a pretty young Congress right now, so I think you need a balance,” Lynch said. (The average US House member is about 58 years old.) “You need some people who’ve been there a while, and you need some new blood too — and we’ve got plenty of that right now.”

That hasn’t stopped Lynch from being a target. National news outlets have labeled Lynch as an incumbent at risk of losing to a left-wing challenger. Roath has out-raised Lynch, pulling in $1.1 million to Lynch’s $817,000 from when he entered the race through June.

Leaders We Deserve, the PAC headed by gun control advocate David Hogg, has sent at least four mailers on Roath’s behalf in about as many weeks, dubbing Lynch “MAGA’s favorite Democrat” and Roath as the candidate who “knows how to fight back — for us.” The PAC has circulated polling showing Roath within 7 percentage points of Lynch. (In February, Roath’s own campaign polling showed Lynch with a 26 percentage-point lead.)

“Congressman Lynch has, no question, a solid base, but it’s a shrinking base,” said Bob Binney, chair of Ward 5 committee rooted in downtown Boston, which has endorsed Roath. “Everyone wants more stand-up people down in Congress, and they don’t see that out of Lynch.”

Lynch is pushing a very different message. A mailer from his campaign framed him as the sensible choice in the middle, asking readers, “When the political extremes drown everyone out, who is listening to you?” — sandwiched between images of two people yelling.

In a recent appearance on GBH’s “Boston Public Radio,” Lynch likened himself to former President Joe Biden, whose “success was his ability to capture the people who elected me, the moderates.”

“We need more people in the middle to give that strength to the Democrats, so that we can actually be a party that governs, and not simply a party of protesters ... against the party in power,” Lynch said.

The race’s dynamic has Democrats divided in places such as Hull, where the co-chairs of the Democratic town committee are split: One is backing Roath, wanting someone “young and energetic;” the other is staying with Lynch, citing his labor support.

Lynch’s union backers, who have stayed with him for years, argue his blue-collar background has made him a champion for workers in Congress.

“There’s a difference between age and being ineffective, and age and knowledge and being effective — and I think Congressman Lynch is effective,” said Chrissy Brady, a Braintree resident and office manager with the North Atlantic States Regional Council of Carpenters, who was among 50 people who waved signs for Lynch outside last week’s forum.

To Crystal Kelly, the Hingham Democratic Town Committee chair, Lynch is “just a regular guy,” which she said, “resonates with the working families that I’ve talked to.”

To be sure, Lynch also pitches himself as an active Trump antagonist. His campaign sent a mailer advertising Lynch’s co-sponsorship of bills to check immigration enforcement. Last Friday, Lynch made an unannounced stop at Plymouth County Correctional Facility, where detained immigrants are held, alongside Representatives Jim McGovern and Ayanna Pressley — neither of whom endorsed in the Eighth District race.

Some Democrats, however, say they want members of Congress to also bring new perspectives, including those from raising a young family like Roath.

“I’m not saying that Stephen Lynch didn’t do that, but his understanding of what life is like for working people is outdated at best,” said Amanda Colligan, co-chair of the East Bridgewater Democratic Town Committee.

That momentum is exactly what Roath is hoping to capitalize on. During the candidate forum in Weymouth — the only time during this race the two have faced one another onstage — Roath repeatedly decried the “politics of the past” and referred to Lynch as a “career elected official since I was about 5 years old.”

“We can’t trust that the system that got us here is going to continue to deliver,” said Roath, a first-time candidate who has criticized Lynch as insufficiently left-leaning on issues including healthcare, immigration, and abortion policy.

What some voters are taking note of, however, are events where Lynch hasn’t been present. At a senior picnic hosted this month by the Brockton Council on Aging, Roath distributed meals and campaign paraphernalia to 300 seniors.

There, he met Fredi Walker, an 85-year-old Brockton resident, who told him she had initially planned to vote for Lynch in her mail-in ballot that week — but would instead go for Roath.

“Life goes forward, not backwards,” Walker said. “Nothing to do with [Lynch] on a personal level — I just don’t think that he’s relevant for this particular time.”